Ken Giller’s paper on conservation agriculture

The following comments have been made regarding the recent paper published by Ken Giller. Ken E. Giller, Ernst Witter, Marc Corbeels, Pablo Tittonell. 2009. Conservation agriculture and small holder farming in Africa: the heretics view. Field Crops Research 114 (1) 23-34. The debate resulted in a number of excellent comments that we would like to share through this blog. I am managing this debate by listing word for word the comments made so far. Hopefully this will be an educational and constructive debate. I have not changed or edited any comment. I encourage any one with thoughts on this subject to submit a comment by inserting it at the bottom of this list of thoughts.

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Dear Ken: I read your well written paper on Conservation Agriculture and agree that there are many issues that need to be taken into account when promoting CA or for that fact any technology, in a developing country and in Africa. Agriculture is a system and it is too easy to ignore the many interactions. However, I kept looking for ideas that you have for an alternative to CA. Many of the issues you raised also apply to present farming systems in Africa but many of these traditional systems have resulted in the poor water harvest, erosion and degradation of soils that we encounter today. The big question is how to reverse these negative trends since business as usual will not make agriculture sustainable and will accelerate the downward spiral in productivity and resource degradation. I believe that the principles of conservation agriculture — minimal soil disturbance, permanent protective soil mulch and rotations (also IPM and other common sense practices) can help on this issue. However, these principles need to be adapted and applied to each location. It is very difficult to overcome the mindset of plowing technology and even more difficult when papers are written criticizing CA. Of course there are issues of weeds, labor, residue competition etc. These are also major issues in the present agriculture. We are supposedly trained as scientists to be able to tackle these issues and develop alternatives. So rather than just criticize CA (which is easy to do), I suggest you should have written some suggestions on what you think would be a better set of solutions. Best regards Peter

Dear Peter,
Thanks for the mail – your comments give me a sense of deja vu. We write in the paper “The response of many CA proponents to such questions is simply to raise their hands and say “but what are the alternatives to CA?”, as if agriculture has no future if all farmers do not adopt CA en masse.”

In the conclusions of the paper we indicate that plough-based agriculture is highly popular among farmers. The aim of our paper is to provide some counter-balance for the huge donor push for CA in Africa at present which does not seem to be matched by farmer demand.

Without increased access to inputs there is little chance of increasing productivity in African agriculture. Sensible agronomy with inputs of fertilizers, good rotations with legumes, integration of crops and livestock etc can improve productivity and soil organic matter and provide an ideal basis for a sustainable agricultural system as practised elsewhere in the world.

We have published extensively on these issues in the past few years and I can send you a list of other papers that highlight many successful approaches, but I would hate to fall into the trap of claiming that there is one solution for all problems of production in Africa. And we do not write off CA totally – but simply point out it is not the panacea that is claimed by many.

It would be good to debate these issues in more depth sometime!
Cheers,
Ken

Dear Ken: Thanks for your email. Unfortunately, the plough based system of agriculture used in Africa is probably one of the main reasons for soil degradation. It exposes the soil to erosion (wind and water), disturbs the biological and physical component of the soil and although it is a way to control weeds, it can also stimulate weed growth. For many African farmers where livestock are not available and farmers must use manual systems it is also a major form of drudgery. I agree that we must not be too rigid in our definition of CA, but the principles of minimal soil disturbance, permanent soil cover and rotations are important and provide a mechanism to reverse degradation. CA can use manual, animal and tractor power. In Zambia, where corridor and other animal diseases have decimated the animal population, farmers spend hours plowing their land manually. I believe the basin system and focusing resources in a smaller area are much more efficient than preparing the whole field. The key is to make the basins permanent and not dig them after the first year. Changing traditional biases and mindsets, however, often prevents farmers from experimenting with new ideas. But I agree this would be a good chance to debate the issue. Best regards Peter

Dear Peter,
I work with a Kenyan scientist – Samuel Guto -who is working on zero-tillage on the slopes of Mt Kenya for his PhD – very similar ecology (soils, climate, slopes) to Western Kenya where we have also worked extensively. On these heavier textured soils the technology certainly seems to work well – no yield penalty and much less erosion. But if you look at the photo below – farmers actually sell most of their residues to be used as animal feed. So – even for farmers without their own livestock there is very little residue to use as soil cover. And without soil cover, zero-till leads to soil crusting etc etc.

Apologies if I reacted strongly to your last mail – but I often have a feeling in this debate that CA advocates seem to think we simply don’t understand and are wedded to ploughing.
Cheers
Ken

Hi Ken: There are many papers published in the last decade that show that zero-till and residue cover reduces soil erosion and increases water infiltration into the soil profile. It was the main reason farmers adopted CA in Brazil and many other countries. I was recently in Western Kenya and observed the color of the runoff water from rains that occurred during my stay and erosion was a major issue. On some of the most degraded low fertility areas we visited, the soil was down to bedrock and there was very little top soil. Ploughing results in the soil being prone to erosion and hence degradation. I am sorry if you took my comment about mindsets as an insult. I was referring to farmers who get mixed messages about ploughing and who traditionally feel that is the only option. I agree they can experiment but will not do so unless someone suggests it would be beneficial. They often can’t envision growing a crop with tillage, until they experiment and see for themselves. The issue of weeds and residues will arise, but in order to cut down on erosion, CA or the principles of minimal soil disturbance and soil cover are vital. So as stated earlier, no problem with your paper, but what are your suggestions for overcoming the problems farmers face in Africa? I am not saying CA is the only solution (although I think it is a good one) but what alternatives do you suggest? We are not throwing up our arms and saying there are no other alternatives, we just want to hear what they are. OK? Peter Hobbs

Guy Evers wrote:
The challenges of adapting the principles of CA in Africa are immense, but this is not a reason not to invest in this approach, especially, at this stage, e.g. in terms of R&D/R4D and building capacity of producers and their organizations. As discussed by colleagues who already responded very well to Ken’s paper, what are the alternatives?

Looks like the paper may be missing some key points; four examples:
1) transition: what are the challenges and implications of shifting from conventional to conservation agriculture? At which stage of the transition have some of the findings, quoted by the authors, been observed? What are the lessons learned from the transition phase under African circumstances?
2) labour, need to discuss not only total labour requirements, also distribution of requirements throughout the season(s) (see for example Haggblade/Tembo Paper on Zambia (2003), quoted by the author, though not for labour aspects, attached for easy reference);
3) weeds: is conventional agriculture the best approach to control/manage weeds with/without herbicides?; Weed management/control aspects are too often neglected, not a CA-specific issue!
4) mechanisation: should we assume smallholder will not access mechanisation? If we assume they should access mechanisation, what would be the best alternatives? Disk ploughing and harrowing? Hopefully not, as viable and sustainable options should be developed on the basis of CA principles.

The paper could include forward looking recommendations. It is not only merely a matter of assessment: much more R4D is needed to develop farming practices based on the CA principles, adapted to farmers circumstances in Africa.

Fred Johnsen, NORAGRIC Oslo wrote:
You asked me about my opinion on the critical paper on Conservation Agriculture (CA) written by Giller et al. and to be published in ‘Field Crops Research’. First of all, I was not aware of the paper, so thanks for sending it to me. I take the liberty to copy this reply to stakeholders in Noragric and CFU as well as your colleagues at NORAD and the Norwegian Embassy in Lusaka, since I expect the topic is of interest to anyone involved in CA. I also attach the paper for the benefit of those on the cc: list who may not have seen it.

The first thing that strikes me about the paper is how the authors characterize their imagined opponents. This starts already in the first sentence of the abstract where it says that ‘Conservation agriculture is claimed to be a panacea for the problems … ‘, a concept that is also repeated in the introduction and the final sentence of the conclusion. Panacea was the goddess of healing in Greek mythology and the dictionary explanation of the word panacea is a ‘remedy for all diseases or troubles’. Everyone who is well informed on the problems of African agriculture knows that they are so diverse and complex that a panacea cannot exist. Moreover, the authors claim that CA is promoted ‘with such strong advocacy that critical debate is stifled’, giving the impression that the authors are among the few who ‘dare to question the doctrine of the established view’, though without outright claiming that they have risked their lives by publishing this critical article. In the conclusion section it turns out that the radical and ‘dangerous’ alternative suggestions that these brave authors come up with is to continue using the plough. In the following, I will leave aside the nonsensical and paranoid rhetoric of the authors and concentrate on the substance of the paper, which actually does merit serious consideration.

The authors define the concept of CA by the three pillars (1) minimum or no tillage (2) permanent organic soil cover and (3) diversified crop rotations. They provide and discuss several arguments that CA may not be the best option in every case:

(1) Mulching may not be the best use of crop residues. This is a valid point to make. In the context of the CAP project in Zambia, it applies particularly to areas with substantial numbers of cattle, where crop residues are used as cattle feed, and in many cases, the crop residues on the fields are grazed communally after the harvest. However, the experience is also that the combination of minimum tillage and crop rotation give most of the benefits of CA, even without the mulching.

(2) According to the authors, the positive yield effect of CA is a long term effect, while no yield effect or even reductions may be experienced in the short run. Factors that may increase or decrease the yield in short and long term are listed in Table 1. This discussion is quite contrary to the experiences from the Conservation Agriculture Project (CAP) in Zambia, where farmers seem to agree that CA gives substantially higher yields from year 1. The main reason for higher yields, as experienced in CAP, is earlier planting because the minimum tillage systems make it possible to prepare the land in the dry season so that planting can start immediately after the rain has softened the soil. This effect is not even mentioned in the discussion of yields in the paper. Is it possible that the authors have based their discussion on experiments where CA fields and conventional fields have been planted on the same day?

(3) Land preparation and weeding under CA are labour intensive. This is a valid point and may be one important reason for the observation that we have made in the CAP project that majority of adopters practice CA only on a part of their land. The authors further claim that CA increases the labour burden of women because of a shift of labour from tillage to weeding. The authors’ assumption is that tillage is mainly done by men and weeding mainly by women, which is the case in some cultural contexts, but not all. This is however clearly worthwhile to look into.

(4) The authors claim that increased soil organic matter is mainly through crop residues left on the fields while reduced tillage doesn’t contribute much to increase in soil organic matter. This may very well be right, but is hardly an important argument against CA.

(5) Large amounts of residues with a high carbon content may immobilize nitrogen in the soil so that more nitrogen fertilizer is needed. However, the authors admit that there is ‘insufficient evidence to conclude whether or not more fertilizer is needed with CA in smallholder farming’.

(6) The authors question whether rotation with legumes can be introduced on a large scale, particularly with reference to limited markets for many of the leguminous crops. However, the authors mention soybeans as one example of a crop that has a ready cash market, and this also seems to be the legume cultivated by majority of the CAP farmers. The point is however valid, and I think CAP has also experienced market constraints for some of the other grain legumes that were introduced.

(7) The authors also discuss soil erosion and agree that CA can reduce soil erosion substantially in the long run.

(8) Biological processes in the soil constitute the final agronomic issue discussed in the paper. The authors agree that the biological activity in the soil will increase as a consequence of CA, but point out that increased biological activity is not always beneficial.

In addition to the above-mentioned agronomic aspects, the authors also discuss the potential of adoption. They point out that many farmers quickly revert to their former practices when project support stops. This is very well known also in Zambia from several NGO managed projects. The paper does not provide any discussion of how the extension strategy and the quality of the extension service as well as the degree of technical knowledge in the organization that promotes CA may influence the rate of sustained adoption. In my opinion, this is an absolutely crucial aspect. Further, the authors point out the importance of a flexible approach with room for adaptations to local conditions and also emphasize that adoption is normally not immediate, but incremental in the sense that farmers start experimenting on a small area and only adopt full-scale after they have been convinced about the benefits of new practices. These viewpoints are clearly agreeable. The same goes for the recommendation in the conclusion section ‘to assess where particular CA practices may best fit, and which farmers in any given community are likely to benefit the most’.

In conclusion, this paper is much more balanced and thoughtful than one could assume from the initial tabloid rhetoric. The single substantial issue where the opinion of the authors differs significantly from the experiences from CAP in Zambia is on the time perspective of yield benefits. The authors express that yield benefits will only be seen after several years, which is also reflected in the following rhetoric question from the conclusion part: ‘How can resource-constrained farmers be expected to adopt practices that in the long term may improve production, but in the short term realize no net benefits, or even net losses?’ On the contrary, the experience from CAP is that CA increases yields from the first year of adoption, and this effect is assumed to be attributable mainly to the effect of early planting.

In the final words of their conclusion chapter the authors claim that ‘there is no case for promoting CA as a panacea’. Again, I believe that the authors are fighting against windmills. Myself, I have never believed that CA is a panacea. But I believe that CA is worth promoting because extension on CA does significantly increase the number of useful tools that farmers have in their toolbox when they strive to construct their livelihoods.

Pat Wall, CIMMYT commented:
Some reflections and comments on the paper by Giller, Witter, Corbeels and Titonell entitled “Conservation agriculture and smallholder farming in Africa: The heretic’s view”.

In common with several of the other commentaries on this paper, once one gets past the sleights and generalities suggesting that proponents of CA are simplistic and don’t understand the issues, there is some good analysis in the paper, although often the interpretation of the data and results is questionable. Most of my comments below are actually covered in the Giller et al. paper, but they generally come to a different conclusion to mine.

Giller and his co-authors have obviously tried to provoke responses, which they have done effectively. However, the paper does not offer any ideas on what systems may be better than CA. So yes, I “raise my hands” and ask “What are the alternatives to CA?” for extensive field crops. There are certainly sustainable solutions for some more intensive systems, including possibly biodegradable plastic mulch, glasshouses, intensive use of farmyard manure etc. but generally these are not feasible for extensive crop production. Some suggest that sustainability can be achieved by adding sufficient manure to conventionally ploughed systems, as can be seen on the small, productive, homestead fields near most farmers’ homes in southern Africa. However, most studies estimate that between 10 and 30 t/ha/yr of manure are required in tropical systems to maintain soil organic matter levels – which of course will require 10-30 full-grown bovines per hectare to provide the manure, if they are stabled and all the manure is captured. Is that sustainable? In the run-up to the Soil Health Workshop in Rome in 2008, Ken Giller wrote that “I actually think, and can back with substantial data, that we can improve soil (chemical and physical) fertility under smallholder farming systems where tillage plays a key role” but that sort of data is completely lacking from the paper.

We at CIMMYT make no excuse for holding to the principles of conservation agriculture and endeavouring to help facilitate it’s widespread adoption – indeed I believe it is both unprofessional and unethical to continue to invest public funds in fine-tuning unsustainable systems and thereby playing with the future of smallholder farmers (in Africa and elsewhere) and the natural resources dedicated to agriculture. Most people would, I believe, agree that tillage is a (if not “the”) major cause of soil degradation – there is a wealth of good, robust scientific evidence to support this, even though Ken Giller (in his response to Peter Hobbs) does not accept this. As such, tillage – although often convenient – is a major cause of unsustainability (or non-sustainability) of present agricultural practices, as is residue removal (whether by carrying, grazing or burning) without the reposition of sufficient organic material and probably also (although this is not conclusive in many systems) monoculture. Removing these degradative components (and not other components such as the need for adequate crop nutrition, weed and pest control, adequate varieties, plant populations etc. etc.) from conventionally-tilled production systems results in conservation agriculture – but finding out how to practically do this under the varied biophysical conditions and socio-economic circumstances of smallholder farmers in Africa (and beyond) will take considerable effort.

It should be obvious to even the most blinkered that agricultural productivity – whatever production system is employed – is dependent upon other factors in the value chain apart from the production technology utilized. Just as tilled the productivity of smallholder agriculture in sub-Saharan Africa is dependent on input markets, availability and affordability of inputs and markets for outputs, CA will be as well. Therefore these issues obviously need to be addressed for future CA systems, just as they need to be addressed for conventional systems – and are being addressed in many high profile initiatives such as those under the Alliance for a Green Revolution in Africa. However, it also appears that one of the major factors limiting input use (by smallholder farmers in sub-Saharan Africa as well as elsewhere) is risk – often risk of moisture-limiting conditions, exacerbated by the reduced infiltration and increased evaporation of tillage-based agriculture. Reducing risk will be a key factor in increasing input use – considerable inputs are often used on high value cash crops (where market price allows more risk-taking) by the same farmers who do not use them on staple cereals.

One of the major reasons for short-term yield depression with CA (where it does exist) may not be so much a problem of the principles of CA not functioning in the short term as it is of not having adapted the techniques for applying the principles to local conditions. Too often researchers, and others, have taken a package of practices used to apply CA in one situation, superimposed the same package in other conditions and (are we surprised?) found that they do not work – or are not as productive as the conventional system that has been locally adapted by farmers over decades. The scientific literature of Brazil during the 80’s and 90’s is replete with peer-reviewed papers showing that no-till does not work – and today there are nearly 25 million hectares of no-till in Brazil. John Lander’s quote from his father (which appears in the dedication of John’s book on no-till in the Cerrados of Brazil) “when practice and theory disagree, practice is always right” is obviously very pertinent.

The need to adapt the techniques for applying the principles of CA to local conditions has three very important corollaries:
1) Farmers should try new practices (including CA) – as they normally do – on a small piece of their land until they have mastered and adjusted the techniques/technologies to their own particular conditions.
2) Research to compare production systems is only valid once these systems have been locally adapted. Thus a researcher should first find out how to properly manage the new system (CA in this case) before he/she can justifiably compare it to the conventional, adapted system. A lot of money and time has been wasted comparing unadapted and poorly managed CA systems with locally refined conventional systems.
3) The suggestion from the Giller et al. paper that it is “imperative that the benefit of each principle (of CA) is properly evaluated” also requires first that we know how to manage the CA system under a particular environment. Only when we have a functional system can we evaluate the importance of the components and, more importantly, the interactions between them, and between them and other component technologies. Yes, smallholder farmers generally adopt technologies in a step-wise fashion but where there are significant interactions between components this may not be possible – just as it is not worthwhile applying fertilizers if weeds are not controlled.

This factor is also important in assessing the impact of CA development and extension programmes. Were the technologies locally adapted, and adapted to the circumstances of different groups of farmers, or just imported – even from local research stations or leading farmers? This may well describe why many projects have failed when projects have ended. If the technologies promoted were not sufficiently robust to have widespread applicability, then interest will probably decline after support is withdrawn – it is the principles of CA that have widespread applicability, not necessarily particular techniques or packages for applying these principles. It is also important that farmers learn what the key components of CA systems are so that they are in a position to understand them and how to modify them.

We share the interest of Giller et al. in many of the problems they describe: competition for residues, communal grazing, nitrogen immobilization, definition (or understanding) of residue requirements, finding out how to live with problems of termites, white grubs etc. etc. etc. However, we understand that these are issues that limit the spread of CA technologies and are actively researching solutions through both biophysical and socioeconomic research. We see them as difficulties rather than insurmountable problems, and are also very aware that widespread adoption of CA by smallholder farmers in Africa will not come easily or quickly – but “difficult” is not a good enough excuse for not starting. I discussed many of the same issues in a paper published in 2007. However the authors chose only to misquote me as simplistically saying that ‘successful adoption of CA depends on “awareness building”’ – no, I stated clearly that CA is knowledge-intensive and that building community awareness of the problems and causes of soil degradation is just one of the many steps in the complex and difficult path to widespread CA adoption. Unless farmers are aware that they have a problem, and that there are possible solutions to it, they will not change.

Giller et al. advocate spending time and money on defining for which groups of farmers CA works and under which biophysical conditions. They suggest therefore that the remainder of farmers (to them the majority) should continue degrading the natural resources with the plough. Implicit in this argument is that they assume that we (those of us working with CA) already know and are using/testing the best techniques to apply the principles of CA in all the sub-Saharan conditions, which of course we don’t. There is another way: instead of just accepting that the CA packages of today are the best that can be applied, and then deciding where and for whom they will work, we should spend the scarce research funds on researching how to achieve sustainable agricultural systems. If there are other sustainable options apart from CA that is excellent – but I for one need to be enlightened. I agree that there may be some areas where CA is at the moment not feasible, and in fact may not be feasible in the future: very dry areas may be one such environment, but I have seen CA functioning in an area with 200mm annual rainfall in South Australia!

Before analyzing the Giller et al. paper “Conservation agriculture and smallholder farming in Africa: The heretic’s view” I would like to start with the following quote.

Innovators should consider that “There is nothing more difficult to plan, more doubtful of success, nor more dangerous to manage than the creation of a new order of things. Whenever his enemies have occasion to attack the innovator they do so with the passion of partisans, while the others defend him sluggishly so that the innovator and his party are vulnerable.” (Rogers, 1983, quoting Niccolo Machiavelli (1513), The Prince). No-tillage/Conservation Agriculture pioneers all over the world have experienced the sad truth of this statement.

In order not to extend this analysis too much I am only going to concentrate my comments to some key issues.

Giller et al. state: “CA is said to increase yields, to reduce labour requirements, improve soil fertility and reduce erosion. Yet empirical evidence is not clear and consistent on many of these points …..”

My 38 year research and development experience in Conservation Agriculture, as well as adequately conducted research, has demonstrated, that yes, yields are in general maintained or increased, labour requirements are reduced, soil fertility is improved compared to conventional tillage systems when the system is properly applied and erosion is definitely reduced! This can not be denied because there are too many examples around the world demonstrating it.

Just to take yields: During a period of 15 years from 1991 to 2004, no-till adoption in Brazil grew (from about 1 million ha) by 22, 6 million ha. In the same period grain production doubled from 57.8 million tons to 125 million tons while planted area experienced only a moderate increase. Certainly other factors as improved technology and better varieties, etc., have had an influence in this sharp increase in grain production, but probably the greatest influence came from applying the no-till technology. A similar situation happened in Argentina from 1988 to 2001 (Derpsch, 2005). This data is much more adequate to illustrate the result of no-tillage on yield then all the research data put together. Also the short-term yield reductions cited in the paper do not need to occur if things are done right from the beginning. The most common reason for yield reductions in the first years of switching to No-till/Conservation Agriculture is lack of knowledge and experience on how to do it. In general the learning curve of farmers as well as researchers in the first phase is in general responsible for these yield reductions. Once farmers and researchers learn how to do it well yields have shown to be equal or better than in conventional tillage systems. See also the arguments analysed below.

The case of labour: Ploughing and tillage in general is the most time and labour consuming operation on a farm. A farmer has to walk 30 to 40 km behind the plough (plus several secondary tillage operations) on each ha. When the system is properly performed substantial labour savings can be obtained. Sorrenson et al. (1997) and Lange (2005) among others, analyzing the economics of the no-tillage system on small farms have come to the opposite conclusions than the Giller et al. paper. One problem in term of economic studies is that there are not many agricultural economists around with enough practical experience to understand CA that are able to do an economic analysis with systems approach.

Soil fertility: There is enough research evidence all over the world to show that when adequately performed No-tillage/Conservation Agriculture systems improve soil fertility compared to conventional tillage systems. If this is not the case it is most probable that research is being conducted without applying the main principles of Conservation Agriculture (e.g. too much soil movement at seeding, no crop residues, etc.). Brazil and Argentina would not have been able to double their grain production in a period of 14 years if their soils would not have improved through application of the no-tillage system.

Soil erosion. The authors of the paper state: “There is little doubt that CA can substantially reduce erosion, although the benefits will mainly be reaped in the long term than the short term”. This assertion reveals lack of understanding of what damage erosion can do. Anybody involved in soil conservation knows that avoiding soil erosion will also bring immediate benefits unless soil losses are minimal.

On the other hand we have to admit that poor research conducted in many parts of the world has certainly given arguments to Giller et al. to come to the assertions made in their paper.

World wide experience and my long experience as a researcher has shown, that in general the same yields or higher yields can be achieved with no-tillage compared to conventional tillage systems. If this is not the case in research plots or in practical farming, the following reasons are generally responsible for that situation.

1) Lack of knowledge or experience on how to do no-tillage/CA. The critical steps to successful no-till adoption have not been followed (Derpsch, 2008).

2) Lack of a systems approach in applying no-tillage. The soil was not tilled but everything else was done the same way as in conventional tillage systems.

3) No-tillage was performed under bare soil conditions or with insufficient soil cover, leading to reduced yields.

4) Lack of experience of the farmer or machine operator at seeding (inadequate regulation of the seeding equipment, the seed furrow stays open after seeding, too deep seed placement, etc.).

5) An inadequate no-tillage machine was used that performed a poor job Inadequate seeding mechanism and seed placement, poor stand, seeds are placed to deep, etc. Research facilities often lack funds to buy adequate machines. All too often conventional tillage seeding machines have been used in no-till experiments! No wonder that yields of no-tillage prove then to be lower.

7) N fertilization was not increased in the first years of applying the no-till system or a leguminous crop has not been seeded previously to provide the nitrogen needed.

Unfortunately researchers in many parts of the world have made and continue to make these mistakes. In general researchers are not good at studying or comparing systems and that is the reason why no-tillage adoption all over the world has been farmer driven and not researcher driven. Farmers are much better in putting new farming systems into practice than researchers and university professors. Researchers in general do not want to change more than one factor at the time on their experiments to avoid interaction between factors and this often makes the results useless when systems need to be compared.

Small farmers in many parts of the world may have difficulties in complying with some of the requirements of No-tillage/Conservation Agriculture principles. But if we surrender after the first difficulties we surrender in achieving our main goal which is to obtain a sustainable agricultural production. In this respect it is frustrating to see that the authors of the referred paper question the merits of Conservation Agriculture but are not able to propose any system that could do better than conventional farming systems. There is no doubt that tillage tools used in conventional farming systems are the main reason for erosion and soil degradation all over the tropics and subtropics and therefore these practices need to be changed. The proposition of Giller et al. that “perhaps the plough would be one possible alternative to CA” reveals the lack of understanding of the authors about the reality of farming in tropical and subtropical environments. Erosion and soil degradation would be the immediate consequence!

Failure of agricultural systems to comprehend the significance of erosion, as well as intensive weathering under hot, humid conditions, has brought about the widespread distribution of poor, badly eroded, infertile soils all over the tropics and subtropics (Ochse, et al, 1966).

I challenge the authors of the paper to come to Argentina, Brazil and Paraguay and ask 1000 big and small farmers that practice No-tillage/Conservation Agriculture in each country if they would consider returning to the plough and conventional tillage practices. If any, they will not find many farmers that will adhere to their proposition to return to the plough.

Another misleading assertion made by the authors that “in the Americas the effects of tillage were replaced by heavy dependence on herbicides and fertilizers” is simply wrong. Except perhaps in the first years of applying the system, no-tillers in North and South America are using less herbicides and fertilizers than conventional tillage farmers.

More than needing further research on defining for which groups of farmers CA works and other aspects of the system as proposed by Giller et al., there is a need for adaptive research and development of the system adapting it to the different environments and socio economic conditions. This needs people with experience and practical skills who believe that sustainable agriculture is possible, not only in the Americas or in Australia.

The damage that this article is going to make to a movement that truly believes in the necessity of a change from soil degrading to sustainable production systems is great. Critique was easy, proposing something better has failed.

It is 13 years now since we launched zero-tillage in India in collaboration with Rice Wheat Consortium and ACIAR. We had very pessimistic views about the virtues of Zero-tillage. Even now we have many scientists not accepting the facts but more numbers of farmers accept this change. Only the process that we followed made a difference. The linear model of doing research does not provide the opinion of farmers. The non-linear model that essentially involves farmers is important. The information contained in the paper has lot of theoretical background on labour requirement, immobilization of nitrogen, rodent problem (when we started some scientists even talked about snakes), water productivity and reasons for yield penalty. There is no mention of small machinery systems that operate with very small farmers in places like South Asia.

Weed problem.

It is very much site specific depending very much on cropping intensity, productivity levels, input use pattern, level of mechanization, cropping system, irrigated or un-irrigated conditions , rainfall and so many other conditions. In some situations where cropping intensity is 200% and production levels are high, the weed population has gone down. The population of weeds like Phalaris minor has gone down. Zero-tillage was used as herbicide resistance management strategy in wheat in North-West India. Yes, it may lead to an incremental change in the favour of perennial if proper agronomy is not followed. Proper agronomy does not mean herbicides alone. It has come as a surprise to say that labour requirement goes up with Conservation Agriculture. Poor initial impression reflected in the Giller et al. paper is too sweeping a statement. Better avoid it.

Water productivity

Well known scientists on water productivity say that if the water productivity is less than the maximum threshold, it is because nutrient and pest management has not been properly employed. Why then every thing is targeted on zero-tillage. In high productivity zones of rice-wheat cropping system Conservation Agriculture (CA) including zero-tillage has improved water productivity. This has happened in clay as well as sandy loam soils. Last 4 years data in very light soils with irrigation has shown that water productivity increases with CA. Giller et al. paper does not definitely prove that the water productivity decreases with CA.

Yield Penalty

Giller et al. paper says that essential aspects like the additional use of external inputs including herbicides and even seed are not counted for quantifying gains. I do not know how to isolate the effect of these factors. Termites eat residue in weeks. Yes, termites always eat residues but how is it related with CA? Some of our farmers say that termites can eat residue but they will leave green crop. Such statements do not provide an explanation for such puzzles.

Decline in Soil Organic Matter

Giller et al. do not agree with the statement from a long-term study which says that zero-tillage will halt the decline in SOM. Factors that contribute to arresting the decline include more biomass and residues. Residues retained on the soil surface contribute more to halt the decline in SOM.

Let us admit the fact that similar effects can not be observed universally. Our job is how to make CA a successful proposition.

Comment from Ken Giller about discussion of his paper:
We are pleased to see the debate stimulated by our article and we have read carefully the numerous responses that have been circulated through the list-server. In addition we received directly a number of positive messages concerning our analysis. There are few substantive points that demand a response in the comments made. As we acknowledge in the paper there are specific conditions, both from an agroecological and from a socioeconomic perspective, that determine the options available to improve soil fertility and crop production.
We are delighted that there is general agreement that CA is not a panacea, and that even where CA may be a viable option there must be a focus on local adaptation of principles. It is heartening to see that this view is so widely shared – which is certainly not apparent from the general promotional material, and has also not been apparent to many of our colleagues working with donor organisations and international and national NGOs.
Given the agreement in the list-server discussion on the ‘panacea’ issue we think it is high time that the FAO revises the text of its website to acknowledge this, and to discuss some of the potential short-comings. The website (http://www.fao.org/ag/ca/) indicates “CA holds tremendous potential for all sizes of farms and agro-ecological systems, but its adoption is perhaps most urgently required by smallholder farmers, especially those facing acute labour shortages”. The website text is uniformly positive, indicating the benefits of CA with few or no caveats.
We indeed hope that our article contributes to debate and will stimulate deeper thinking on targeting and adaptation of CA in Africa, and that farmers may benefit from the many positive attributes of CA systems.
Finally – we were interested to read a conclusion that resonates with our paper in a recent article by Rattan Lal on the plough:
“Adoption of NT farming by resource-poor farmers of South Asia and sub-Saharan Africa is constrained by removal of crop residues for fodder and animal dung as residential fuel, lack of appropriate seed drill which can sow in an unplowed soil covered by crop residue mulch, and non-availability or prohibitively high cost of herbicides. While use of the plow is unsustainable on erodible soils, its use is essential until alternative sources of residential fuels are available to rural households, efficient seed drills are developed by village blacksmiths, and herbicides become economical and effective against perennial weeds or other viable options of weed control are available.”
Title: The Plow and Agricultural Sustainability
Author(s): Lal, R
Source: JOURNAL OF SUSTAINABLE AGRICULTURE Volume: 33 Issue: 1 Pages: 66-84 Published: 2009
With best wishes,
Ken Giller, Ernst Witter, Marc Corbeels and Pablo Tittonell

Comment by Ken Giller after several comments sent:
Dear Pat, Jim,
Thanks to Pat for taking the time to comment on our paper. I note from Jim Findlay’s response that some people are getting fed up with the debate and indeed it’s perhaps time that Amir calls a halt to the discussion – up to him. However I have yet to be convinced that there are flaws in our analysis as Jim indicates. We would like to share a few (last?) thoughts:

1. The reason that we wrote our paper and submitted it for publication in a peer-reviewed journal – Field Crops Research – was for two reasons. Firstly a feeling that much of what is written on CA is not peer-reviewed and suffers the problem of perpetuating opinion that is poorly backed with evidence, so we wanted to submit our ideas and arguments to the process of peer review. Secondly, that we felt all criticism of CA was being conveniently ignored by the proponents.

2. Pat indicates that in our paper “often the interpretation of the data and results is questionable.” but does not detail what the problems are. If Pat or others find fault with our analysis we encourage him/them to write to the Editor of Field Crops Research to communicate these problems to the general readership. Otherwise, (and please forgive the pun) you run the risk of “preaching to the converted”. We have received many compliments and thanks from colleagues in both research and development in Africa and elsewhere for our article. A common comment has been that it is high time for a critical analysis of CA. Perhaps a wider readership would be interested in reading your thoughts.

3. The plough – Pat writes “They suggest therefore that the remainder of farmers (to them the majority) should continue degrading the natural resources with the plough.” The plough is an inanimate object, and as such we think cannot be blamed for causing soil degradation and erosion. Of course the plough can be misused, and poor practice due to the misuse of a tool obviously can cause problems. There is no statement in our paper in which we promote environmental degradation.

4. In terms of the issue on sustaining soil organic matter contents I think we are in agreement that it is difficult given the constraints under which farmers operate. But the point we make is that the amounts of soil organic matter are controlled mainly by the amount of organic matter added to the soil, and tillage plays a minor role. The effect of tillage on soil organic matter stabilization in the long term is relatively small. The paper from Pat’s own research group (Govaerts, B., Verhulst, N., Castellanos-Navarrete, A., Sayre, K.D., Dixon, J., Dendooven, L., 2009. Conservation Agriculture and Soil Carbon Sequestration: Between Myth and Farmer Reality Critical Reviews in Plant Science 28, 97–122.) shows that enhancement of soil organic matter by CA is found in only half of the reported cases.

5. Given the poor productivity in much smallholder agriculture then without inputs there is little chance of building soil organic matter, and yes we agree that there is not enough manure around for all fields. The critical lack of inputs is indeed common to tilled systems and CA. But where fertilizers are used and enough crop residues or other sources of organic mulch are available, then soil C can be built with or without tillage. Indeed soil C can be built more rapidly with tillage since residues are ploughed under and no longer consumed by cattle.

6. I just re-read Pat’s paper (Wall 1997), and indeed we misquote by implying he used the term “awareness raising” when he actually states that “community awareness activities” are needed. Apologies for this. But the point remains in what Pat writes in response to our article if there are problems with CA then it is simply because we have not done enough fine-tuning, and that if sufficient effort is invested we will find a CA solution for all. We agree wholeheartedly that “we should spend the scarce research funds on researching how to achieve sustainable agricultural systems” – our point of disagreement, on which we have to agree to disagree, is that we do not accept this can only be achieved without tillage.

7. Christian Roth made some thoughtful and very useful comments in an earlier mail on this topic which we think could form a very useful starting point and framework for further analysis of where CA has most to offer, and where it is best to invest in other approaches.

Dear Ken,
Congratulations on a thought promoting paper. I am a no-till enthusiast from Australia, with the nick-name “no-till Bill” and the website http://www.no-till.com.au but I am also proudly an B. Ag. Sci. Graduate with a M.Sci. in soil nutrition. I have travelled widely, including taking Australian farmers to see no-till on about 8 separate trips globally (two to South America). I am also friends with many South Americans. The South American cover crops idea with disc seeders only and maximum stubble retention has been promoted widely in Australia and the science data generated (myself included) has been ignored as cover crops have been shown to make no economic sense (in Australia, in contrast to Brasil and Paraguay where more than 2 crops per year are common).
I doubt that I will say anything to you of significance – I just want to write and say thanks. It is an interesting and complex set of issues you raise. The need for poor farmers to make a profit every crop has to be their highest goal – agreed! The need for sustaining the soils resources (or improving them) is, while important, less significant than a families need for life. All agreed! I have very little understanding of the type of agriculture you speak of – other than as an interested tourist and an agricultural student.
The sad thing is that experts from elsewhere believing that their specific CA approach is the best one for all regions. There is a nice ring of acknowledgement in your introduction “assist in identification of windows of opportunity.” Although in CA promoters defence, often people who argue against no-till have been unscientific in their enthusiasm for damming the technology to stem the tide. As you effectively point out adoption is the proof of a technology that works in a region/environment.
Good luck with your paper and the subsequent discussions that will no doubt follow.
Bill Crabtree

Comment from Howard Buffett:
Dear Ken,
I have read some of the correspondence and thought a comment about your reaction to “mindset” might be worthwhile. My perspective on this comes from 28 years in a tractor. I have no-tilled for the last 18 of these years and farm 1240 acres in Illinois and 6,000 acres in South Africa. Our foundation has also funded about 30 conservation based ag projects in Africa and Central America (background).
Every system of farming has its unique challenges. As genetics change and bugs and diseases move geographically, the challenges and opportunities present themselves. Brazil is of course a great example of CA – and U.S. farmers have demonstrated innovation from the early no-tillers back to the 1940’s to Strip till and combinations of organic benefits applied to large production systems.
Back in 1994 there were 38.9 million acres in no-till in the U.S., now it is at least 66 million representing 20% of U.S. crop land. This growth must demonstrate there are benefits. I have strayed a bit from the point I wanted to make – mindset.
I have had 3 farmers sit in a tractor with me over the years while I have taken my mulch tiller to the field to clean up winter ruts – often from anhydrous knives as a result of a heavy rain as the frost comes out. Each time they have said “Howard, just do the entire field”. When you challenge them and ask why, the only answer they provide is “it looks better” or “that is how we have always done it.” A third comment from some no-tillers who no-till on their own ground is that landlords will not let them no-till – the landlords say they are not working hard enough or it doesn’t look clean all of the time.
My own mindset change had to be both, not working the field and being able to stand looking at weedy fields for the first 4 or 5 weeks of growth. You get over it when you learn the benefits but unfortunately a lot of farmers quit before they see the benefits. On our farm in Nebraska (which I now rent out) we have 2 corners out of our pivots that are Luten silty clay that is very difficult to no-till – but then there is no good way to farm gumbo! The balance of the farm is excellent for no-till, so you’re correct, no-till, just like any other farming technique will not work 100 percent of the time. However, there are many benefits to no-till or other minimum tillage systems given the time to understand them and the willingness to adapt – again, this can be mindset!
There is a significant mindset issue with any change – that is true with many things. No-till can be seen by some as a radical change. In the emerging countries, no-till is a risk if you have been plowing all your life, a risk that can end in the death of a child if it produces less food. This would certainly create a mindset challenge. Therefore, mindset is of course an issue – I see it every year when I plant a crop and I see it between those groups in Africa who have fallen in love with mulching and those groups who scoff at it. There are obviously many ways to farm. My personal experience in both the United States and in Africa is that CA, no-till, mulching, basin planting, whatever you wish to call it, has many benefits and has concretely helped many small resource poor farmers.
I still love the smell of my neighbors freshly turned black dirt here in Illinois (even though it makes me cringe), that is when I stop for a minute and consider how fortunate I am to have the opportunity to farm – to put my hands in the dirt, to nurture crops and I certainly appreciate that I have a choice how I do it. Everyone should have a choice – but if you do not know the options or cannot afford to try the options, then it isn’t a choice.
No one believes that CA is a panacea – if anything is insulting it is that individuals who understand agriculture believe there is any silver bullet. There are sometimes strong agendas against changing farming techniques – so do we need to fight for change sometimes – yes. My choices in this country – as a farmer – have been reduced, they are controlled by a handful of companies who have a different mandate than I do, so I would never want to force this on anyone else – but I will keep trying to provide options to farmers whose lives depend on improved productivity, and my choice will be to provide them with knowledge of minimum-till based systems – and why wouldn’t I!?
Best regards,
Howard

Comment from TF Shaxton:
The article is well-written, informative and provocative, but ultimately (in my personal view) not particularly helpful, for three main reasons:

1. Rising worldwide problems are being caused (singly and in combination) by ongoing climate change, land degradation, increases in population and in the associated demands by people for food, other agricultural products and water. In many situations the sustainability of the productivity of soils – (as environments in which roots grow and water moves) has become diminished by inappropriate use and/or management.

In the past, the effects of long-rotation ‘bush fallows’ served to maintain the balance between damage to soils resulting from the tillage phase of various agricultural systems and restoration of soil architecture and replenishment of plant nutrients in the root zone. As economic pressures built up, on e.g. commercial farms the use of ‘grass breaks’ in formal rotations served the same general purpose, but more quickly. Well-implemented Conservation Agriculture (as defined [lines 122-127] in e.g. Brazil demonstrates the capacity of CA to both restore and maintain the productivity of soils, under favourable conditions, on a self-renewing basis integrally and continuously within the production system itself.

It would have been more valuable had the authors identified the characteristics, dynamics and synergies in these optimum soil conditions as the ideals to aim for in other situations. It is the generation,(and/or regeneration where necessary) of these beneficial soil conditions, by appropriate means, which should be the goal. The combined use of the three interacting techniques used to characterise CA (as at lines122-126) appear to be most capable of producing these effects.

For a great range of agro-ecologic and socio-economic reasons, in the conditions of smallholder farmers in Africa the uptake of CA is likely to be relatively slow because of the large number of people who will make decisions whether or not to change. A farmer’s success on a small scale e.g. near the homestead (line 124) in improving food security and its variety has been shown to result in expansion of the treated area both within the farm and among interested neighbours. It is from these small manageable beginnings that wider improvements are likely to spread, if broader constraints imposed by problems of transport, markets, availability of appropriate advice, etc. are effectively removed.

2. The authors have not given much attention to the detrimental aspects of continuing with tillage, whose excessive use can result in accelerated rates of oxidation of soil organic matter and damage to optimum conditions of pore-space, due to pulverisation and/or compaction of soil layers. Runoff and erosion are primarily consequences and symptoms of such problems, more effectively addressed by improvement in conditions of cover over the soil and of soil porosity – in the context of conservation-effective agriculture – than by physical ‘SWC’ works alone. The activities of the soil-inhabiting biota (including plants’ roots) are key factors in maintaining and recuperating plant-favourable porous soil architecture, as attested by farmers and by photographic records.

3. It is not clear how closely the authors adhere to the definition of ‘CA’ (as at lines 122-127) when commenting on its effects. For instance, at lines 353-356 they write of ‘CA systems subjected to continuous maize production ……’; and in Footnote1 point to ’the confusion as many different practices tend to be lumped under this general heading’. This confusion continues within the paper, reducing the cogency of the authors’ criticisms.

The authors make many valid points, but I would have preferred the second-last sentence of the Abstract to have been re-phrased to pose the question:

‘How can socio-economic conditions around smallholder farming in SSA be improved so as to favour farmers’ strengthening of soils’ ecology and productivity – such as can be achieved through well-managed CA – in even the most challenging situations?’

Farm families which are resource-poor and services-poor on the African continent and elsewhere urgently require answers.

This represents an extensively researched article quoting over 100 references, written by four authors and critically reviewed by an additional six anonymous referees. It was first read by some following the circulation of a well developed draft over a year ago. This final pre-publication text circulated by CA-CoP has no doubt been developed over a period of at least some 18 months – most probably very much longer.

The article aims to assist in understanding when and where CA is most likely to be beneficial in SSA and discusses which farmers and under which circumstances they are most likely to be able to adopt CA approaches with a successful outcome.

There is a lot of sense contained within its observations and indeed highlights many of the concerns, or perhaps better phrased, the main focal points which have often already been identified both by promoters and critics for future research and development efforts together with investigating ways to deal with the implicated policy issues.

But does it add anything new? Are we surprised that it is taking time to take off in SSA? The rise in its adoption in South America was exponential and let us not forget the considerable funding impetus accorded during this process by, in particular, the World Bank. And even today, there are important areas and regions where it has still not been adopted, even partially. In Africa, progress is steadily being made – and not only in the three countries mentioned in this article.

The take-off in South America was largely farmer led and much of the effort in SSA has lately been focused on assisting farmers to try to apply the principles within their own socio-economic, agro-climatic and cultural environment. Farmer Field Schools, on-farm research programmes and other participatory methods are being attempted. Sadly, little concrete field data has so far been generated at the farmer level and this is certainly an area which needs increased attention. Information exchange is also improving as field experience is vital – research may have to catch up later.

The article, almost certainly purposefully, contains a certain phraseology which provokes a response, not least because some of the facts are highly questionable. I will only mention the most glaring.

The word panacea has appeared in discussions relating to CA for a number of years but I cannot recall a single occasion when it has been used by an author or speaker in conjunction with the advocacy of CA practices. I have however, frequently heard or seen it used by them in the sense that CA should certainly not be considered a panacea for the problems faced by smallholder farmers.

Another aspect which is commonly emphasised by CA proponents is that there is no magic formula which can be applied, and this may to a considerable extent explain some of the apparently paradoxical evidence discussed throughout the article.

And the plough ………! Edward Faulkner had a hard time to convince many back in 1945 , even the author of his Forward. In fact direct planting is very widely practised in Africa, particularly in the Sahel when after a good rain, a myriad of farmers stride out onto unploughed land, armed only with a hoe and drop the seed into place. Of course yields are disastrously low because so many other important agronomic aspects are not dealt with – here is perhaps a great opportunity for the CA approach as already one of the “pillars” is already accepted.

And finally, residue burning! Perhaps it is sufficient just to mention that most would not hold the views expressed in the article (“…other important reasons for burning include fertility enhancement, weed/pest management …….. or hunting).

1. I will here defend the technology of Zero Tillage, which is the preferred one within the broad definition of Conservation Agriculture.
2. The use of the word “heretic” in the title implies that Dr. Giller considers ZT as a religion, which is already a ploy in polemics. This is wholly unscientific, since the principles of Zero Tillage do not involve any superior being.
3. Many points of agreement that I have with this paper are superficial, when you dig down the situations presented have other possible explanations :
a. Zero Tillage cannot be seen as a panacea, or magic cure. Why, because it requires good local adaptive research, persistence in discovering the reasons behind failures and belief in making the basic principles work, they will not automatically overcome all extraneous constraints. The panacea idea encourages oversell by inexperienced extension agents, induces negligence of one or more key factors, leading to below-par performances. In Brazil, we have always conquered the problems which arose in ZT because we knew and believed in the principles;
b. Many constraints to uptake are not technical and therefore non-technical solutions (i.e. political and economic) are required. The paper, however, confounds technical and non-technical reasons for failure and proceeds to generalize on the non-applicability of ZT, rather than analyzing these two categories apart (as it demands for the individual elements of the ZT technology);
c. There is a need for more analytical research which separates out the yield factors in ZT under African conditions.
d. Yield reductions are possible in the first few years of Zero Tillage (i) if hard pans are not eliminated – the comparison with minimum tillage ripping is biased if there was a hard pan not removed under the ZT comparison (ii) if N immobilization is not counteracted by a legume cover crop or additional N fertilizer (an added cost which can be offset by higher yields) or (ii) before the re-structuring of soil has been adequate to remove re-densification of soil in the absence of tillage (upland rice is extremely susceptible, but soybeans not). These negative aspects must be offset by the economies of erosion control on the farm (i) by accounting for the elimination of re-planting or stand loss due to water or wind erosion (cotton seedlings are highly susceptible to damage from wind-blown sand), (ii) costs of removing erosion damage or cultivating around gullies and (iii) accounting for the lost nutrients in erosion runoff. Off farm government policies need to place a value on (i) the cost of silting of reservoirs and rivers, (ii) reduced costs of maintenance of earth roads, (iii) improved health from elimination of dust and ash in the air and other cost savings generated when ZT is adopted on a wide enough scale, especially reduced food costs and improved yields in drought crisis years;
e. Further work is needed to identify the causes of the often-observed short-term yield reductions and how they can be avoided. I fully agree, provided that the investigation covers all the points mentioned in 7. below.
f. “Identification of the situations when CA can offer major benefits is a challenge that demands active research”. Totally agree; the corollary is also true, identification of the constraints to remove to make CA viable, whose costs should be considered a long term investment in the environment by a society which wants a sustainable agriculture.

4. The principles of Zero Tillage have universal application, however, the solutions are local. If Dr. Giller has unearthed some cases where the package did not work and he has pinpointed principally non-technical factors, this requires a policy decision by governance (i.e. formal or non-formal, local or national) to overcome the extraneous limiting factors, e.g. cattle grazing on stubble – this one requires the supply of an alternative food source to allow a political solution for graziers’ rights and avoid a range war..
Seeing the huge success of tropical ley farming in Brazil, where crops pay for the residual fertilizer which renovates pastures, one wonders whether this system could not be demonstrated on a large-scale experiment/demo in Africa where there is adequate rainfall for maize. This would establish the principal of livestock farmers and crop farmers gaining from the synergy of collaborating on such a rotation. In Brazil, a joint venture between cattle owner and crop residue/winter pasture owner is common,
5. Dr. Giller´s references include only one in French and NONE in Spanish or Portuguese, so his literature survey is quite incomplete, when he excludes two countries in the vanguard of world Zero Tillage technology for small farmers, Brazil and Paraguay whose experience can illuminate much for the humid and sub-humid zones of Africa. This is reinforced, since the paper nowhere cites Séguy (surely one of the most relevant researchers worldwide in ZT), or his experiences in Madagascar, or the Ivory Coast experience where cotton farmers built a 60 km live fence to keep cattle off their cotton fields where they were practising ZT or Mrabet´s experience with ZT wheat under low rainfall and heavy clay soils in Morocco…
6. The statement in the introduction that “widespread adoption in the Americas, where the effects of tillage were replaced by heavy dependence on herbicides and fertilizers” is misleading : while the dependence on desiccant herbicides is true, the net effect of Zero Tillage adoption is a reduction in total input use through the greater efficiency of the ZT system, especially in terms of soil biological activity and, more important still, a reduction in the net negative impacts on the environment of these herbicides, by exchanging desiccants with the lowest of all GUS ratings for the previously-used pre-emergence herbicides with a far greater potential for groundwater pollution. The HUGE off-farm impacts on mitigating the effects of erosion, dust clouds, GHGs, aquifer recharge and flood damage (see a very rough calculation in Landers et al., 2001) have engendered World Bank projects based on ZT adoption in four southern states of Brazil, which represents a public investment to assist farmers in achieving sustainability. This approach appears to be sadly lacking in Africa, Later in the paper these off-farm benefits are recognised, but they need to be linked to social transfer payments to farmers in recognition of the cost-savings generated for society;
7. If some exponents in the field do not respect the fundamental principles involved in Zero Tillage adoption, obviously there will be lack of success. I agree with Dr. Giller that the worst thing that can happen is to market Zero Tillage as a panacea, where farmers often adopt by hearsay and don’t obey the caveats associated with the conversion process that we have always advocated in Brazil:
• maintain crop residues on the surface;
• remove soil compaction;
• remove nutrient and acidity constraints;
• start small and learn by your errors;
• get expert advice;
• check sprayer and planter performance before use;
• learn how to mark out for spraying;
• add extra N for gramineous crops

8. It is very easy to throw “heretical” stones, but an approach which attempts to develop ZT technology and policies for small farmers by learning from constraints identified and unforced errors in application of ZT principles and another to develop ZT without the use of herbcides (also important for organic farming) would be a far better use of Dr. Griller’s time than to criticize from the sidelines. I have struggled with getting Zero Tillage to work and then to improve it for 33 years, miracles don’t exist I agree, they need hard work before they pop up. There is a Brazilian (socialist) song which says “He who knows chooses the hour, he doesn’t wait for things to happen”. Also most of the breakthroughs come from farmer ideas and observations, however uneducated a farmer be, his observations are pure gold when you sift them out from interpretations made with limited knowledge, and don’t get hung up on unreplicated data, just talk to more farmers and get an aggregate position. My father taught me “when practice and theory disagree, practice is always right”.
Apart from the permanent legume mulch principle which I developed in 1988-92 (Vasconcellos & Landers (1993), the best thing I have seen in the humid tropics is a little-publicized technology developed by a revolutionary thinker where ultra-high density trees or woody shrubs are cut at ground level (no re-sprouts) with over 50 ton/ha of biomass, total weed suppression and extremely high food crop yields. APDC is open to support to develop these technologies.

9. “But under more humid conditions and on poorly drained soils the same effect can cause waterlogging resulting in yield depression.” I have never seen this phenomenon, always in Brazil, the re-structuring of soil by leaving crop residues on the soil improves internal drainage – plough pans must be removed before adopting ZT. This case needs further investigation. Likewise the poor results on sandy soils – in West Bahia we have had this problem of soil cementing when inadequate mulch is present, but as soon as it rains the soil becomes penetrable for roots. Again a case for deeper investigation, I would suggest.
10. There is no separate organized analysis of problems by biomes or climate zones or soil types, although these variants are mentioned briefly in the text. The attached simplified climatic map (Wikipedia – Sub-Saharan Africa) gives a reasonable summary of climate zones/biomes (sand coloured – desert; yellow-semi-arid; light green – savannahs and dark green- rain forest. Disregard the dates, which refer to finding Iron Age artifacts).
11. “Thus the suitability and adoption of a new technology in one place as, for example, observed for CA in South America does also not imply that the conditions for adoption necessarily exist in SSA (Bolliger, 2007; Gowing and Palmer, 2008).” This statement needs clarifying. Here we MUST differentiate between technical solutions and solutions to economic and policy constraints. We are shooting the best alternative for sustainable farming in the foot if we accept defeat because external constraints limit success. We need to learn how to motivate politicians, donors and international agencies to assist in altering policy to create an environment in which the ZT/CA technology can flourish, by removing extraneous constraints. That is a real political problem which has to be faced up to, but it is not a technical argument against CA or ZT. Only good real farm data will convince –the NGOs and foundations cited were doing their part in demonstrating what can work technically. If policies can’t be arrived at to capitalize on this, then the problem is not the technology. Small farmers can perfectly well enter into the inputs market if the technology generates better financial returns. Policies to solve market, transport, price, etc constraints, plus on-farm research to maximize returns from outside inputs, are required to make the new technology viable.

12. I attach a graph from Lucien Séguy, whom I rate as tops in ZT research in the sub-humid and humid tropics. It clearly shows the yield response to volume of surface biomass and would have answered Dr. Griller’s claim that the drivers of yield are not separated out. APDC has done over fifty on-farm demos which show definitive response to gypsum in corn with small farmers using animal traction and a variety with a potential over 7 ton/ha plus inter-row establishment of pasture with Brachiaria spp. That would solve the feed problem for African cattle in sub-humid areas but the trade-off is the need for Glyphosate to desiccate before the next crop – is that too bad? Or this practice could be itinerant until enough fallow was converted to pasture.
13. If someone gives me a Euros 25,000 scholarship, I could produce a scholarly paper more fully elucidating possible ways forward, also questioning some of Dr. Giller´s assumptions and claims. Right now, on a Brazilian minimum salary pension, it is a bit difficult and I have spent too much precious thinking time on this already.

Some comments on a thought-provoking contribution to the debate on conservation agriculture’s relevance to the smallholder farmers of sub-Saharan Africa. By Brian Sims, 18 August 2009

Make no mistake, this is a useful comment on the impact that conservation agriculture (CA) can have on the livelihoods of smallholder farmers. What, perhaps, it lacks is a global view of the consequences of our current abuse of the planet, and the role that CA can make in alleviating the situation. The impending crisis, brought about by inappropriate agricultural practices, the exponential rise in population and the, already present, impacts of climate change have the potential to produce a perfect storm of starvation, desertification, flooding and destruction of irrigation water sources. This is not the time to stand on the sideline and wonder what went wrong. Action is urgently needed.

Although the paper makes many valid points which will greatly enrich the debate on the application of CA principles to smallholder farming systems; at the same time some areas need further clarification. As far as I know, CA has not been presented as a ‘panacea to agricultural problems’ and, of course, never should be. Rather it is a concept that aims to conserve resources whilst achieving sustained high production levels profitably. Contrary to the view expressed in the paper, rather than blindly accepting the benefits, researchers are industriously working on clarifying the issues surrounding the impacts of CA. A review of contributions to the 4th World Congress on Conservation Agriculture held in New Delhi in February of this year will confirm the world-wide efforts being made.

Some other points need further clarification. One is that CA will result in increased labour demands for crop production, particularly for weed control. It is a pity that the paper’s authors did not use the excellent IFAD/FAO study on labour saving with CA as it would have exposed this as a fallacy which needs to be addressed. Tilling the soil not only results in structural damage but also brings up new seed banks year after year. Weeding in sub-Saharan Africa is predominantly women’s work and the burden causes great suffering every cropping season ‒ up to 60 person-days per hectare of back-breaking drudgery. CA, on the other hand, prevents this annual renewal of weed seeds in the top soil and, together with the permanent soil cover provided by cover crops and mulch, actively suppresses weed germination and development. Of course, some hand labour will still be required, for surface scraping and roguing to eliminate any infestations. Herbicides can also clearly play a part when required, as emphasized in the paper; but there is very little discussion of weed control with leguminous cover crops and no mention at all of one of the region’s favourites, Dolichos lablab. The CA weed control options for smallholder farmers in SSA are embraced and summarized in Chapter 7 of the IIRR/ACT manual directed at this audience and lamentably not mentioned in the paper.

Whilst most of the important issues are dealt with in a thoughtful and thorough way, there are several other contentious issues which deserve deeper analysis, for example: the soil fertility and structural improvements contributed by soil biota; the issue of burning biomass for (very) short term convenience and gain; the immense impact of the increased erosion of tilled soils on their fertility; dealing with the provision of cattle fodder in crop-livestock conflict situations; the tremendous potential of fertilizer trees like Faidherbia albida; and so forth. However the overall impression given is that we are accepting the status quo and raising our hands in submission, rather than getting on with the urgent tasks of marshalling our resources and looking for solutions to identified problems.

Business as usual is not an option if we are to confront climate change with practices for adapting to it and mitigating its effects. And what about the planet’s 6.8 billion population which is still climbing inexorably and leaves 30% of SSA’s people hungry today?

The last few seasons saw the introduction of Conservation Agriculture (CA) as part of agricultural support programs in southern Africa to increase food security and productivity of small holder households. Impacts of CA interventions have been remarkable, farmers practicing CA could increase their yields significantly compared to farmers not using CA, often doubling sometimes tripling yields.
Undoubtedly this impact is due to the initial focus on land preparation (Conservation Farming, mostly hand dug planting holes for poor farmers without tillage), in combination with improved land and crop management, optimising available resources and some fertilizer.
The huge impacts of the –still limited- CA interventions (the numbers of farmers supported are still very low) , has created some hype where some stakeholders seem to see CA as a “quick fix” or panacea to all problems of small holder farming in SSA.

However, all CA practitioners have been warning against this strongly, there is no absolutely no doubt that CA is an excellent and working technology that will increase yields and income of farmers if done well and supported correctly, but it will not achieve results over night and will need a concerted approach by all parties involved.
Also in this context it is important to state, CA is not the magic potion or, panacea, not even a quick fix to the problems affecting small holder farmers. But CA is a high potential cure, if prescribed and taken correctly to increase and stabilize farmers’ production in general and especially small holder farmers.

Problem Statement:
The main problems limiting yields, income and improvement of the status of most small holder farmers are among others: inappropriate (or should I say poor) agricultural policy, declining investments in agriculture, unreliable rainfall, low and non viable producer prices, poor extension support, poorly developed input supply markets, shortages and high prices of key inputs, limited or no market access, no or unaffordable credits and insecure land tenure.

Other major problems affecting small holder farmers are, tillage constraints, declining soil fertility, erosion and commonly poor land and crop management. Addressing these shortfalls will and does increase productivity significantly and CA is addressing those! Some of the above reasons could certainly also be addressed through conventional farming approaches, but not all and not as comprehensive as trough CA!

CA in the field
The single biggest problems for many small holder farmers are limited or no access to any form of tillage or timely tillage and poor agronomic practices. Through CA even farmers without any tillage can still prepare their lands timely and accurately (planting holes) and will plant crop at the correct spacing and depth. In smaller CA plots farmers are also managing their crops better. Those famers with access to draught power can use rippers and planters, increasing areas to be planted and reducing their costs. CA is allowing farmers to plant timely and utilizing the full potential of the season and also reducing the risk of soil erosion drastically. Solving tillage and erosion at the same time is already more than enough reason to promote CA!

The plough is not an alternative any more at all, since:

• Many farmers do not have access, or timely access to a plough or any means to pull it.
• Ploughing is expensive (it costs about the equivalent of 1MT of maize/ha, therefore even with increased labour costs CA is more economic).
• Soil erosion is much higher.

Additionally, there are remarkable and documented yield increases in CA, even if some of those have to be attributed to fertilizer (which some none CA farmers do not have), but that still does not change the impact. It is correctly argued that a major contributor to the above is timing and simply the application of good agronomic practices, which is theoretically not tied to CA, but is in practice!

However, timely planting without CA is plainly not possible for most farmers as they do not have tillage means. Therefore yield comparison has to take average planting date into account, in which is in average 4 to 6 weeks delayed in farmer practice, which does attribute that yield increase to CA!

The appliance of good agronomic practices again can not necessarily be claimed by those promoting CA, but –to my knowledge- CA is the only agronomic practice introduced to farmers as a package and focusing strongly on extension.

CA Limitations:

1. It is a technology for crop based farming systems and does not address the challenges of many livestock and mixed farmers (which it is not meant too).
2. Many farmers will only be able to do the full CA package (mulching, reduced till and crop rotation) after some considerable lead time, therefore the maximum impact of CA may be realised slower than expected. Still improved timing, improved management and precision application of fertilizer will give significant returns.
3. CA is attempting to change mindsets and traditions of farming (zero till without plough), which will take some considerate time and effort.
4. CA is a farmers technology not a researchers playground, farmers need to be shown and explained in the field, which again is very time consuming and slow.
5. CA is no “quick fix” it needs coordinated approaches by all stakeholders and buy in by governments and policy makers.
6. Small holder farming will only strive, even with CA, if complementing measures (as described in the 1st paragraph) will be also taken up.

Despite the above shortfalls CA is an excellent technology and proves much better in the field than any farming method currently practiced by small holder farmers in the region. It is increasing and stabilising yields in most crop based small holder farming systems, but it is very labour and extension intensive to introduce. Still returns are higher and costs per unit product are lower than conventional farming! Most farmers will over time adopt the full package of CA if timeframe set for CA are realistic and will than increase the benefits of CA even more.

Conclusions

CA is being promoted throughout sub-Saharan Africa as part of a solution to low productivity levels, reducing smallholder farmers’ vulnerability to drought, addressing low draught power ownership levels, and combating increasing levels of soil degradation and loss of fertility.
Since 2004 the CA approach has been promoted to more than 40,000 small holder farmers in Zimbabwe, through a combination of partnerships with government, NGOs, donors and farmers organisations and has consistently increased average cereal yields by 50 to 200 percent.

The CA approach is based and depending on a strong and comprehensive extension support, rather than simply handing out free inputs to farmers. This approach enables farmers to apply inputs (water, fertilizer, and seed) more efficiently and sustainably. The higher input efficiency of CA provides higher and more sustainable productivity gains needed to achieve better food security in small holder farming systems. As much as CA provides swift improvement of yields it can not be a short term intervention, but requires coordinated long term support by all stakeholders involved.
CA has proved to be a very appropriate tool to increase production and productivity of, especially resource poor farmers, significantly and improve food security, livelihood and incomes. Through the cooperation with the ministry of agriculture CA has been mainstreamed into agricultural extension and measures to expand CA to all farmers have been taken. Further developments will include the introduction of mechanised CA methods for “better of” and larger farmers.

CA is no panacea or magic potion, not even a quick fix to the problems of small holder farming in SSA, but the best we have at the moment. The appropriate expansion and rolling out of CA has the potential to transform many subsistence based farming setups into profitable and sustainable interventions. The introduction and controlled growth of CA complemented by appropriate extension, inputs and credit schemes will increase and stabilize agricultural production significantly. This will enable many more households to achieve and maintaining food security from local production and be able to start producing surplus. Furthermore CA is a more sustainable practice and more economic. But, in promoting CA the wider framework conditions have also to be taken into consideration to improve small holder farming systems.

I was very interested in your paper. I think it is a timely issue to raise, and given the flurry of emails and comments, it seems that your somewhat polemic choice of the word ‘panacea’ has got the discussion going.

Reflecting on your paper and the comments made so far, I am wondering if the discussion has missed a few critical points and is being conducted somewhat at cross purposes. I will try and elucidate.

CA principles
I think that your paper and subsequent comments do not distinguish clearly enough between some of the underlying process principles, and the CA practice principles. The origins of CA reside in the desire to control soil erosion and reverse soil degradation. In a nutshell, at the process level the key principle is to avoid a loss of soil infiltrability due to soil surfaces without mulch or canopy cover being exposed to raindrop impact and subsequent soil surface sealing. There is ample evidence in literature, starting with Duley’s classic work in 1939, that shows that surface seals control runoff generation in most situations. The exception is shallow soils that quickly become saturated and where runoff is generated through saturation overland flow, rather than Hortonian overland flow in the case of surface seals – that is why in some cases there are reports that on steeper slopes, where we are more likely to encounter young, shallow or truncated soil profiles and saturation overland flow is the primary cause of runoff, irrespective of whether the surface is covered with mulch or not, runoff will occur. In fact, it is the mulch that primarily avoids surfaces seals being formed – theoretically you could continue ploughing a soil, but as long as you covered it immediately with 100% residue cover, you would unlikely experience any significant runoff. Conversely, ZT-planted soils without mulch can also exacerbate runoff and soil erosion. So from a point of process principles, in most cases ploughing will continue to be the main problem of runoff generation, by virtue of surface sealing in the absence of surface cover.

The second desired important process to consider is that of soil carbon accumulation. This occurs in a combination of adding additional soil carbon, and reducing mineralisation by reducing soil aeration following tillage operations. This is the basis on which crop-ley systems have evolved and it is where the ZT benefit kicks in – the reduction in mineralisation is probably as important as the accumulation of additional organic matter through mulch and additional root biomass production using green manures. While I can think of papers that have attempted to quantify either process or more often the case, lumped both together, there are probably not many robust studies around that untangle the relative contribution of organic matter accumulation vs. reduction in tillage-induced mineralisation. Maybe more research needed here.

The critical point in all of this, and which I feel has been disregarded both in your paper as well as most of the responses I have read so far, is that the rate of the above processes is very significantly rainfall dependant. Most of the CA revolution in South America has taken place in high(er) rainfall areas (>1200 mm) compared to a lot of areas in SSA (and South Asia, and Australia), where not only is rainfall lower (400-600 mm), but it also becomes a lot more variable (and this introduces risk, which is a separate issue to be discussed below). In simple terms, the more rainfall, the more likely you are going to get runoff and the more effective CA becomes in controlling erosion. Also, the more rainfall you have, the more biomass you can produce, and the greater your OM addition will be, and the more likely there will be fertility related yield benefits under CA.

And this is precisely the nexus between process and practice which I feel has not been sufficiently considered in your paper and the ensuing responses. The CA practices evolved initially under higher rainfall (and more fertile soil) conditions in South America and have turned into CA principles (ZT, rotation, mulch). These you challenge with respect to their universal applicability in SSA. In fact, I would contend, the process principles still remain valid, but there are undoubtedly threshold rates below which process rates become negligible to have significant short term benefits. These thresholds in biophysical terms directly depend on rainfall as well as indirectly depend on rainfall through more or less biomass production. They then are further compounded by farmer practices such as feeding residues, further reducing process rates (of OM accumulation in this case). Merv Probert carried out a neat little modelling exercise to try and define some of these thresholds (pdf can be downloaded at http://www.aciar.gov.au/publication/TR66). In fact, Merv’s work suggests that in low-input systems of SSA, you might actually not achieve net OM accumulation, even under CA ! So here there is certainly a major area requiring further research, and you actually also point this out in your paper. In fact, it would go towards helping us understand where CA is likely to work more easily and, achieve quicker benefits of farmers.

So, let’s stop confusing process and practice principles. In areas with low rainfall, rotations become a bit problematic if you have barely enough water to grow one main (food or cash) crop. This becomes even more challenging if you are on low fertility soils with yield levels of about 1t/ha of biomass, and where in addition farmers have through necessity legitimate alternative uses for residues. Not a lot of carbon to accumulate, making it hard to adhere to the CA practice principles in the form they have worked well elsewhere.

CA as a cropping dominated paradigm vs. the need to look at livelihoods
I think the more valuable part of your paper was section 4 onwards, where you discuss the need to consider the broader livelihoods context of small-holder farmers in SSA – no argument with that. A key difference between the successful CA practice in South America and the direr parts of SSA and South Asia is that in the former we are mainly looking at commercial, crop dominated enterprises (even small-holders using CA in Brazil produce for the market). This contrasts starkly with small-holders in SSA, who are predominantly subsistence farmers, working under very different sets of choices, very risk averse and with low capacity for change and adoption. The need for immediate returns on investments (be they as modest as a bag of fertiliser) in the face of highly variable climates precludes quick and easy solutions to adapting CA practice to these dry and low fertility environments. Getting farmers to retain residues in this environment is not a matter of policy – it is a matter of lowering risk. It so happens that keeping livestock is one of the key risk mitigation strategies of farmers in dry environments (also true of the highly developed Australian farms based on wheat-sheep systems). So, if we want to promote CA principles of practice in drier environments, we have to do this in the context of farming systems including a recognition of the role of livestock, as well as understanding that in these circumstances farmers also consider labour trade-offs for off-farm employment and migration to secure livelihoods, making labour intensification (e.g. weeding) problematic.

So where to from here? – definitely not the plough, although we might still have to live with it for a few years. Merv’s modelling shows the way – we need to raise the overall fertility levels first, initially with low dose fertiliser regimes suited to the low capacity for investments, so that we progressively start getting above the critical net organic matter accumulation thresholds, and eventually we get the system to trend upwards again. Once the systems stabilises at a higher productivity level (and not necessarily yet using CA practices), we can provide options for farmers to start splitting the use of residues between partial retention and partial feeding. Just as process rates are slower, we also have to tackle CA with a far longer horizon in mind. Eventually, we can replace the plough by minimum tillage with partial residue retention – and that maybe is as good as it gets in some parts of SSA, South Asia and Australia – and then that would constitute CA commensurate with the local physical and socio-economic conditions.

Dear Rolf,
Thanks for your message, your attachment on infiltration and erosion, and the kind invitation to visit CA systems in Latin America. I (Ken) would love to take you up on your invitation though I am not sure when I will get the chance. Among our authors Pablo Tittonell is from Argentina and knows the agricultural systems of South America well, and Marc Corbeels has worked in Brazil and is moving back to EMBRAPA Cerrados in December and may have more opportunity to meet you.

In our article we do not discredit CA in Latin America, nor do we suggest that farmers who have adopted CA should return to the plough. We do question, however, whether CA fits well in the smallholder farming systems of Africa.

“….as if agriculture has no future if all farmers do not adopt CA en mass. Perhaps one possibility is the plough – and it may be worth evaluating with farmers how a technology relatively new in historical sense in SSA has become so widely a central part of farming practice.”

This in my view is a clear suggestion to use the plough and it is notably the only alternative to CA that you put forward in your whole paper.

I consider myself a development worker. I am a German citizen who has worked for international organisations. At present, I am employed under a local contract (not in an international organization) by a South African University in a project to introduce Conservation Agriculture (CA) in the Eastern Cape Province, South Africa. As a development worker, my goals and intentions are to assist the financially-resource-poor rural population in improving their lives and livelihoods. I am not a technical CA specialist, but I see CA as a practical and appropriate tool for development. At the same time, my work (especially in the field) does not allow me to sit down and write a lot, and therefore, please excuse the late reply to your paper. Likewise, I am not an academic, so please excuse my non-academic writing style.

My own experience is as one of the very few who has worked in, and studied, CA projects and practices both in South America (Paraguay and limited in Brazil) and in Sub-Saharan Africa (South Africa and to a lesser extent, in Lesotho and Swaziland). This work with smallholder farmers is the basis for my comments. I will attempt to reply to some general issues in your paper, as well as some of your more technical points. It is therefore a mixed response, one that addresses particular issues raised in your article and also offers some general comment, without suggesting that it is a complete reply to all the points in your paper.

Before I start to comment on your paper, I would like to give four examples to which I will, in analogy, refer to in my text. These lessons I extract from these examples are necessary to make my points clear.

1st Football:
Football is regarded as the most popular sport worldwide. I would now apply your approach and break down football into its principles (the technical ones).

Firstly, we could divide football into (1) passing; (2) defending; (3) shooting at goal; (4) running; (5) goalkeeping; and (6) heading, for instance. If we then, secondly, examine each of theses principles, then we would find that only passing the ball would not generate any goal, consequently, any match that relies only the principle ‘passing’ would end scoreless. Just ‘defending’ would generate a similar result, because if each team just defends, no goal would be scored. Shooting at goal can only be done by one team at a time, since only one ball is used. However, the question remains how does the shooter get the ball? ‘Running’ is another very ‘boring’ principle, because if all players just run, I might go to an athletics competition, where athletes probably run much faster. The fifth principle of ‘goalkeeping’ can be one of the more spectacular ones to watch since everybody likes a good goalkeeper executing spectacular saves. But, again, were does the ball come from to make these saves? And lastly, ‘heading’ needs somebody to lift the ball off the ground before it can be headed. Heading on its own is not much of an exciting activity.

Broken down into principles isolated from each other, principles that are not integrated with each other, this analysis presents football as a very boring game that could prompt me to wonder why is it the most popular sport in the world? Should we instead follow another, more exciting sport? Here, I will not mention or discuss which one, but simply disregard this discussion. However, football does not seem to be an exciting sport.

Anybody who likes football or knows anything at all about the game, will instantly (i) see through my absurd attempt at trying to criticise football by breaking it down into separate ‘principles’ of the game; and (ii) insist that the game needs to be seen as a system, where all of the above principles are applied simultaneously.

2nd Car Driving:
In 1995, about 9,000 people died in car accidents in Germany (where cars were invented). The two most common causes of these accidents were drunk-driving and speeding. This death-toll could support the argument that car driving is very dangerous and should, therefore, be abandoned in favour of another means of transport. Of course, nobody demanded this, because it seems clear that the unfortunate incidents resulted from ‘bad’ practice of driving, not from driving per se. Accordingly, instead of outlawing car driving, the authorities adopted an educational approach instead, be it through awareness campaigns, improved training or through penalties to teach people to drive better.

3rd Time:
Only recently, on the CA CoP mailing list in the display of two photos, did Herbert Bartz, one of THE CA pioneers in Brazil, receive an acknowledgement from the Brazilian President Lula. This high profile recognition was for Herbert Bartz’s 25 years (!) of contribution to Brazilian agriculture. The point that I would like to raise here is that the current acceptance of CA in Brazil required 25 years (actually 37 years) of adaptation and constant, on-farm experimentation for CA to be identified with successful commercial farming. It took 18 years to bring 1 million ha under No-till.

Time–required for local adaptation and validation by farmers–is a critical factor in development work. The experiential learning required to know how to fine-tune and apply a set of general principles to local circumstances takes more time than most are prepared to allow for CA adaptation in SSA.

4. Expert
CA in SSA is most often applied by people who (1) have never seen long-term CA, i.e. do not posses a vision and (2) have never worked in a medium-term CA system, i.e. by those who lack CA experience and skills. In my experience, this often results in a poor application of CA as the many examples in your paper attests.

Surely, this example has to be seen in conjunction with the Car Driving Example: you condemn CA when you should be condemning incorrect implementation.

I will now discuss some general issues raised in your paper.

In your introduction you state that: “In addressing these questions we aim to enrich the debate around CA and smallholder agriculture to assist in identification of ‘windows of opportunity’ in space and time to which efforts on CA could be focused”. (lines 112-115)

While I agree that a more lively discussion on CA is needed, I also believe that the emphasis needs to be on the real, practical constrains of CA adoption and adaptation, and the demonstrable benefits of CA. Therefore, I appreciate your article as a promotion of a discussion that is long overdue; mainly for development-political reasons and also to clarify what CA really is. However, with reference to my “Car Driving” and “Expert” example, I am deeply concerned about the way that your article confuses the uniformed way that CA is practiced with the intrinsic merits of CA per se.

First of all, your general discussion of CA and its adoption in Sub-Saharan Africa (SSA) by smallholders appears to me very often a comparison between ‘apples and oranges’ (not even pears). In most cases, when the CA from South America is used in examples, the CA referred to is the mechanised version of CA in Brazil, Argentina and, perhaps, Paraguay. This comparison between sophisticated, mechanised CA in South America with smallholder CA in SSA is, of course, incorrect.

However, the situation of smallholders, let’s say, in Paraguay, Colombia, Bolivia, or Northern Argentina, is not so different from the circumstances of smallholders in SSA. For example, when, for SSA, you state that “Key resources that are constrained are land, labour at key periods during the cropping cycle, feed for livestock, manure for soil amendment, money to invest in external inputs, and lack of markets for produce”, the same applies to South America too. In both locations weak infrastructure, limited (if any) access to financial resources, poorly equipped and motivated extension service, lack of markets, etc. are prevailing constraints among smallholders in both SSA and South America.

The questions that should be asked more often in Africa are, (i) why and how did the CA smallholders in South America overcome these constraints first; and indeed (ii) did South American smallholders actually overcome these constraints or are they adopting and adapting CA despite these constraints and if so, how? Even Bollinger et al. (2006) in their paper stated that resource-poor farmers have developed a variety of different adoptions of CA. I am sure that there are enough examples that could be looked at in South America, suitable for the SSA situation.

Before further commenting of specific issues addressed in your paper, I want to clarify one thing first. You state in chapter 2 that “To achieve this, CA is based on three principles that are believed to enhance biological processes above and below the ground. These are: (1) minimum or no mechanical soil disturbance; (2) permanent organic soil cover (consisting of a growing crop or a dead mulch of crop residues); and (3) diversified crop rotations”. (lines 121-126)

This is not quiet correct. What is correct, is that the FAO ‘definition’ states that plant association in the case of perennial crops are part of the system AND that these principles need to be applied simultaneously and continuously. These latter two are very important provisos and hence your inquiry about which principle of CA contributes to the desired effects is not correct. I refer here to my Football Example, which aims to establish the principle that holistic strategies cannot be dismantled and discussed in terms of isolated tactical parts. (The synergistic contribution of N in the well-known interaction effect between N, P & K in fertiliser experiments cannot exist or be measured in isolation or outside an experiment based on a simultaneous, factorial set of treatments.)

Furthermore, the FAO definition is not a recipe and it has its origin in on-farm field experience and, to a much lesser extend, on experimental research field/stations, but it was not made up in an office or laboratory or library. The CA definition is therefore based on practical evidence and not on beliefs or principles ‘measured and discovered’ in a priori ‘expert’ research. In fact, I would personally not even consider it to be FAO’s definition at all, but a statement based on common sense.

“The constraints for farmers to adopt all principles of CA as a package make it imperative that the benefit of each principle is properly evaluated …” (lines 161 -166)

At this point, it might be interesting to address another question. Why can’t farmer adopt all principles as a package? The answers of course are known since modern development work started in the 50s and 60s, and are stated by you in lines 89 to 92. Therefore, do we deal with CA specific problems or de we deal with development problems in general?

In my opinion, all developmental problems or constrains (whichever is the better/applicable word) need to be overcome for smallholder farmers, and comprehensive, inclusive solutions have been stated by e.g. Haverkort (1991, p. 4-5) as LEISA experiences:

Haverkort’s points are a result of more than 20 years experience in developmental work in Africa. LEISA was ‘introduced’ because conventional, high yielding practices did not improve the lives of smallholder farmers. We can also see from this example that several approaches need to be applied together of which e.g. CA would be one.

The problems of development are complex and need comprehensive (not complicated) solutions. Soils are complex too and so a multidisciplinary approach for dealing with soils in the way that CA does, has widely demonstrated to provide solutions to complex soil problems.

CA is about improving production through improving soil ecology and soil biology and we know that these are, by their very nature, complex processes that we actually do not fully understand, any approach that considers a holistic solution would, most probably, be more suitable. Thus, we need to see CA as a systems approach that cannot be broken down to separate tactical items measured in isolation of each other–a point I emphasised earlier.

To those who counter that research station experiments could unpack the contribution of separate CA factors I would say: please show me the factorial set of treatments you include in your field trials, and simultaneously ;-) , prove to me that your experiment station research represents any situation other than only the circumstances prevailing at the research farm at that time.

Indeed, the very questions your paper now flags as needing ‘research attention’ begs the question: ‘Why did expert research not ask these questions 37 years ago before a farmer, Herbert Bartz, started doing the real research that is today, the foundations of CA? It is difficult to avoid the conclusion that ‘expert, upstream research’ is desperately trying to verify what thousands of farmers on millions of hectares the world over have already proved: CA exists as a discrete way of farming, it is profitable (a farmer’s proof of concept cleaver instead of ‘peer review publishing’) and (simultaneously ;-) ), it preserves natural capital and mitigates climate change.

Now permit me to make a few comments on some of your points raised.

3.1
“In regions where farmers own few livestock, such as southern Malawi, parts of Zambia and Central Mozambique, …” (lines 229-233)

In my own experience, many smallholders in Paraguay stated the problem of livestock intrusion on CA farms, admittedly on a different scale than here in South Africa or Lesotho. For instance, one will understand that e.g. cattle is a supply of income, milk products and/or meat in South America, too, which is the same as in SSA. And yes, crop residues were and sometime are still burned in Paraguay in traditional cropping systems.

3.3
“If CA results in a strong shift of labour required from tasks normally performed by men, …” (lines 346-349)

Wouldn’t this be a problem in any development activity, e.g. value adding can be women’s work, consequently, increased yields can be seen as increase of labour to women. Is this desirable or not? Likewise, and based on pure logic, higher yields mean longer harvest hours. Are higher yields therefore also undesirable?

I am not playing down the importance if the issues associated with increased women’s work, but I believe we rather need to find a shift in peak labour demands (such as at planting) and try to mitigate this, by reducing the peak labour time. Well, CA can just do this, by reducing labour force required for planting, for instance. And wouldn’t it be good to see a shift in cultural habits too, away from discrimination against women? And yet, due to the terrible impact that diseases, e.g. HIV and AIDS, have in SSA, many women are left behind, forced to do men’s work also, such as planting. Under these SSA realities the easier planting methods enabled by CA adoption surely deserve applause as a potential solution?

“In one of the few long-term assessments of conservation tillage practices in SSA, Vogel (1995) found that CA systems subjected to continuous maize production led to unacceptable infestation with perennial weeds within 6 years”. (lines 353-356)

This is a paper that assesses CA but it is internally and logically flawed inasmuch as it purports to examine an example of a ‘CA system’, but focuses on a system of continuous maize production. This creates a contradiction in terms because correct CA systems use crop rotations (at least 3, but better 4 year rotation of the same crop on the same spot ). Hence, this is an invalid and contradicting argument. I refer to my “Car Driving” example.

“This reflects experience in North America, where perennial broad-leaved and grass weeds became increasingly problematic with reduced tillage despite the use of herbicides…” (lines 356 to 359)

To use an example from North America (mechanized and commercial) in order to assess potential for SSA (hand or animal and subsistence and, at best, semi-commercial) seems inappropriate to me. You are, at least, ‘guilty’ of comparing apples with oranges.

“Although it may be argued that absence of an adequate mulch of crop residues may have exacerbated weed problems in these trials, it is clear that restricted access to agricultural inputs such as herbicides…” (lines 362-365)

Indeed, inadequate mulching seems to be the problem and restricted access to agricultural inputs is a constraint, but not only limited to herbicides . The recommendation for beginning with CA, derived from South America, is to convert very small portions of land to CA (ideally starting with 10%), and then hand weeding becomes less of a problem. It seems to me that the research did not understand CA and the experiences and recommendations from South America, and consequently their trials were not appropriate. I refer here to my “Expert” example. But yes, absence of mulch and absence of rotations as in non-CA systems, do contribute to increased weed infestation, which is quiet logical.

“A common claim by the proponents of CA is that no-tillage with residue mulching will halt this decline and leads to accumulation of SOM”. (lines 381-383)

I would not use this as evidence against CA, because, yet again, it refers to incomplete CA, because (informed) proponents of (simultaneous, holistic) CA would insist on adding crop rotations to no-tillage and residue mulching. If a defining factor of a holistic system is removed, one doesn’t need a peer reviewed publication to show that the overall system will disappoint. Hence, the example you use is not talking about CA, but at best, about “no-till with soil cover”.

However, research outside of CA confirms that no-till and mulching independently reduces decline of SOM, as you state in lines 404–408. One has to keep in mind that also the quality of mulching is very important, some residual mulching can actually have a reverse effect by creating a non-breathing layer.

The increase or decline of SOM is a question of balancing inputs and outputs. If returns of dry matter of crops and green manure cover crops to the soil is insufficient for a certain agro-ecological condition, than in any system there will be a decline in SOM, albeit this decline will be exacerbated in a tillage system. And yet, if we now add consideration of the reduction of labour due to not ploughing and the increase in earthworm activities (the natural ploughs), then not incorporating organic matter seems logical. Again, CA is a system and assessment of CA needs to be done as a system, considering a suite of components and advantages. But, here I repeat myself.

3.6
“Crop rotation forms a central pillar of CA, and many approaches highlight the use of cereal–legume rotations …” (lines 490–508)

This is a very interesting part of your paper. To me it indicates some very fundamental problems CA agriculture scientists/researchers in SSA demonstrate. Firstly, the crops that are mentioned are fine, nothing wrong with it. However, I am bewildered to see that a crop sequence of groundnut/maize/maize is called crop rotation. A crop might be grown for 2 years once, but then a break of several years needs to follow. As I understand the example used by you, groundnut/maize/maize is followed by groundnut/maize/maize and so on. Perhaps, I misunderstood something, but perhaps in a scientific paper this should have been explained.

Furthermore, what is the aim of development work with smallholder farmers? Risk reduction, food security, then surplus production in order to buy those products that cannot be produced (e.g. salt). Then one could aim at more surplus production, potentially to pay education and health bills, for instance. If the homefields are used for crop rotations, and, in fact, that is where large parts of the food crops are produced, why weren’t the crop rotations or even the CA system assessed on the homefields? Here in the Eastern Cape, we even insist that farmers should start exactly there.

Some advantages of practicing CA on homefields include: better land husbandry–possibly because of shorter walking distances, control of livestock intrusion, control against theft, etc. In fact, the best CA systems are those that are highly diversified. Crop rotations and inclusion of legumes (and vegetables) contribute to diversification, resulting in risk reduction, which is one of the fundamental survival strategies of smallholders, especially for those farther away from the “tarmac”. And the more crop species that can be sold, the more the risk reduction for markets. The lack of markets, again, has nothing to do with CA, but is a general problem, even for conventional production.

One thing to keep in mind: do you propose that smallholders should produce just one or two crops, year after year? If so, it would be a highly commercialised approach, in which a specialisation of production takes place. Yet again, you are comparing apples and oranges.

“One approach that has proved to be inherently attractive to farmers and is standard practice in much of southern Malawi is intercropping maize with the grain legume pigeonpea (Cajanus cajan (L.) Millsp.)”. (lines 519-522)

Correct and very important. In fact, one of the recommendations and practices from South America is intercropping of these crops, which are called GREEN MANURE COVER CROPS (on purpose). As you stated, they provide N and can serve as food, fodder, fuel and cash crops. Intercropping is not restricted to pigeon pea, but can be done with almost any crop (e.g. velvet bean, lab-lab, cowpeas, pumpkin, sweet potatoes, etc.). I know of other examples, even including cassava, vegetables, fruits, cereals (like rye, wheat and oats). However, as you correctly emphasize this, we can see again that the SSA application of CA is far from the South American smallholder experience (please refer to my “Expert” example). The golden rule is (in no particular starting order): legume => grass (such as maize, sorghum, cereal) => tuber/vegetable/other broadleaved (could be for 2 years) => legume => grass, etc.

“Future emphasis on cereal–legume rotations for CA should focus on multipurpose grain and fodder legumes, although expansion of their cultivation will depend on the availability of ready markets for the quantities of grain produced beyond the direct needs of the farming households”. (lines 552-556)

Doesn’t this count for any developmental/agricultural intervention? And by the way, please see above for golden rule of crop rotations. Just cereal-legume is not a real rotation, but a crop alternation or crop sequence and people do not live of cereals and legumes alone: they need mixed cropping that includes more than just two crops.

“There is little doubt that CA can substantially reduce erosion although the benefits will mainly be reaped in the long-term rather than the short-term”. (lines 572-574)

Yes, but not quiet correct. Erosion can and does continue on CA farms, but only on those that badly practice/manage CA, e.g. when mulch is not sufficient or is neglected, or when they, as you recommend, unpack CA and focus on only one of its components at the expense of the synergy generated by applying all the principles of CA simultaneously.

There is research done in Brazil on this, which was already presented at the 2004 Soil Conservation Congress in Santa Maria, Brazil. Please see my comment on “Car Driving”. Additionally, especially on slopes, even in the short-term, soil erosion is reduced significantly, especially in comparison to conventional tillage systems. Those slopes are often, not always, the marginal areas, where financially-resource-poor farmers live.

“Nhamo (2007) clearly shows that there is more abundance and activity of soil biota under maize-based CA cropping systems than with conventional practice in the sandy soils of Zimbabwe”. (lines 584-586)

I question here again, is this really CA when you talk about a maize-based system? I understand that a maize-based CA cropping system is a monoculture maize system, which is not CA, but I have made my point before.

And, if the maize-based system is central to your arguments, you should have unpacked it and demonstrated what its components are.

“Use of crop rotations is a well-recognized approach to reducing the risk of building up pest and disease problems, which may be exacerbated when crop residues are retained in the field …” (lines 597-612)

Please see my comments above. In a good CA system, the same plant species should actually not enter the same field for 3 to 4 years. And yet, using an example of a no-till system and of incorporated legumes or maize straw in order to assess the potential of CA seems to be incorrect.

“We therefore conclude that it is important to realise that enhancement of biological activity in the soil as a result of CA may not always be beneficial, but can result in effects detrimental to crop production”. (lines 613-616)

If your conclusion is based on incorporating straws and assessing CA based on no-till monocropping systems, then perhaps you are right. Nevertheless, you assess an apple by looking at an orange. To me, your conclusion is illogical based on the evidence used.

4.
“There are many experiences where adoption claimed during the course of active promotion of technologies by NGOs and research later transpired to be due to the temporary influence of the project, rather than a sustained change in agricultural practice”. (Lines 621 – 625)

In the development work, this is commonly known as a Donor Syndrome and is not restricted to CA. I would suggest that this has more to do with the approach to development interventions (as stated before) than with CA. In an academic paper, I would have expected that the authors have a look at the other side of the coin and also consider the donor syndrome.

4.2
I agree in principle that traditional land-use rights can be an obstacle to the introduction of CA, especially the establishment of mulch throughout the season. However, in my experience, the traditional land-use systems can present an obstacle to rural development in general and is therefore not a constraint restricted to CA. For instance, the overstocking in the Eastern Cape Province, South Africa, is anywhere between 250 and 450% (statistics based on estimates). The resulting erosion, soil compaction and competition for crop cultivation (for food and cash) are vastly visible and extend even to peri-urban and urban areas (within squatter camps, Daily Dispatch from 9/10/2009). Should we now sit and accept this or is there, perhaps, a change in attitude towards livestock required? I refer to my example of attitudes towards women’s work.

This is another point on research I would like to raise: why after 15 years of CA in SSA did nobody come up with a livestock strategy? I assume that livestock has been a problem in other development interventions (not CA) in the past. At the recent CA World Congress in India (February 2009), I attended the session on livestock inclusion. For me, I did not see a solution yet, but, the research was done by agricultural scientists and not by people who are specialised in working in participatory extension approaches–for several reasons I might imagine. And yet, such a strategy was immediately discovered and proposed by our CA trainees (government extension officers), albeit conditional on the proviso that this would take several years (at least 5–10). It is simply a matter of ‘convincing’ the community of the value of mulch and presenting them with alternative fodder. This needs to be done in practice, on fields and in communities and it is again a Time question. Who has got the time required in development work? I refer also to my “Time” example.

4.3.
“Given the complexity of the CA management packages…”(line 734). I do not agree to this statement, which is made by many African CA experts, too. Quiet contrary, what is required in CA, is very old and traditional knowledge that needs to be revived; even the Chinese and Greeks B.C. have practiced crop rotations and used green manure crops.

Direct planting (minimum soil disturbance) can be done with a planting stick, which has been used for centuries, or a hoe. It is indeed very simple and can be cost-free on a smallholder level. What is often confused with CA knowledge is good farming practice or improved farm management. In-time planting, availability of proper seeds (preferable family-owned, traditional seeds) and good land husbandry (e.g. weeding, IPM) are amongst them and, again, not restricted to CA. I would suggest that if the farm management practices are improved, even under conventional crop planting, farm performances would increase. I can see that a technology (if we can call CA this) that is based on ecological processes, can be more complex, nevertheless, living in harmony with the ecosystems is something that smallholders have done for centuries. CA is therefore actually based on traditional and indigenous knowledge.

And, if Green Revolution technologies are heralded as the solution for African smallholders (which I question highly), based on MODERN external inputs, then I can see a need for a much bigger management and knowledge package (which seed does well with which fertilizer, etc.–ignoring the costs here).

Additionally, as Bunch (1982) in his very good book “Two Ears of Corn” already stated, agricultural development with smallholder farmers is a process in which inventions should be introduced slowly, hence CA would need at least 3 to 4 years for a correct introduction on a sound foundation. And yet, we as experts do expect smallholder farmers to adopt/adapt all three principles within a shortest period of “Time”, not even considering the middleman (i.e. extension officer, who has to learn CA, too), which adds on to the total time of adoption/adaptation.

“Failures of extension in SSA are often due to a combination of a lack of relevant technology, failure by research and extension to understand and involve farmers in problem definition and solving, and weak linkages between extension, research, and farmers…” (lines 742-746)

This is exactly the case, and so assessing CA based on previously poor research and implementation of CA, is not fair and correct Unfortunately, these bad examples are used throughout large parts of your paper. I refer to my “Expert” example here.

“Restrictive definitions of what constitutes CA rather than flexibility with consideration to the local conditions are therefore in the long run more likely to hamper rather than promote adoption of complex technologies such as CA…” (lines 746-749)

This advice that your own paper would be well advised to held and implement, but of course, such consistency isn’t compatible with setting up straw men and then setting them alight and (simultaneously ;-) ) claiming that the light of the fire represents ‘insight’.

To repeat: the CA definition used by FAO is a distilled description, at the level of principles, of what has succeeded in practice. It is not restrictive at all, but it only states WHAT principles to use and not HOW to start experimenting on/with their implementation, as long as this is done continuously and simultaneously. These principles are based on sound ecological principles and are in harmony of fundamental laws of nature.

The point I tried to illustrate with my ‘Football Example’ is that the 3 principles go hand-in-hand; they are synergistic components that lose their synergy when they are separated from each other. Just as a football player has the freedom to choose HOW to pass, head, kick, run, or defend, without being able to choose to NOT do these things together, so too can the CA farmer adapt the principles of CA as longs as he finds the best mix of all three, and add GMCCs to the equasion. This, as we know from football, makes the difference between successful and unsuccessful football teams. Consequently, the question is not WHAT do adopt, but HOW to adapt and to realize that any ‘treatment’ applied to any ecosystem is a ‘solution’ that is critically specific to the relevant system in question.

“As with other complex crop management technologies, adoption is unlikely to be immediate, but will be incremental, with farmers experimenting on small areas and only adopting on a large-scale when they are fully convinced of the benefits of the new practices. …” (lines 751-768)

This is very, very true and should, maybe, have been used before in your paper in an assessment of the adoption of CA in SSA (see also my previous comments regarding Bunch’s book and the 10% adoption in the first year). Because, many of your literature examples used (including or especially the research and demonstration plots) did not consider it. This I see as a confirmation of my previous comments on “Car Driving” and “Expert” and “Time”, arrogance of many researchers, bad extension service, development as a business, and people without a vision and expertise, etc.

A very basic question that we have to ask ourselves is: what do we think is good for farmers? In other words, is what farmers do sustainable? This might seem paternalistic. I agree that we can only offer to share our knowledge with farmers and if they do not want to accept it, then I am happy to leave the farmers in peace. At the end, who am I to tell grown-ups, who have several kids, what is good for them and what they should do? This is an ethical question of how to do development work and should be discussed more widely, but not only among CA practioners.

5.
Knowler and Bradshaw (2007) concluded on the basis of a world-wide study that there was a lack of universal variables that explain the adoption of conservation agriculture…“ (lines 804-811)

Clearly Knowler and Bradshaw (2007) meant to say parameter and not variable? This is also a distinction that your paper misses resoundingly.

But Knowler and Bradshaw (2007) are correct, because their assertion is consistent with the agro-ecological principles stated by e.g. Altieri (1987), which, for instance, work with systems, cover crops and diversification of agro-production, all of which must be adapted to the local conditions (site-specific).

“There are many different types of CA,…” (lines 819-820)
Again, this is not quiet true, there are many ways to implement CA, but the three principles are not negotiable and must be applied simultaneously and continuously.

“Direct seeders have a high equipment cost, although there are cheaper alternative such as the jab planter”. (lines 821-823)

Again, this is not true, planting can be done with a planting-stick (I mentioned it before), which is free of costs. The problem is that many ‘experts’ are afraid of introducing ‘backward-technology’ within development interventions. I refer here to my “Expert” example.

“In his review, Bollinger (2007) highlighted that nobody is questioning if CA should be adopted by farmers when analysing the reasons for the lack of uptake of CA in South Africa”. (lines 836-838).

Unfortunately, you seem unaware of the CA project examples that Mr A Bolliger had a look at in 2005 . One of them suffered a typical donor syndrome, the second one was a mere CA demonstration, and the third one was never a CA project per se, in which CA was a component, while mechanical maize production was the main aim. In the last two examples, the extension approach used was bad, if at all existing, and only very rudimentary CA training was provided to extension staff. This fact was criticised by Bolliger et al. in 2005. The two projects were not development interventions, but typical “experts-knows-best-modern-hybrid-high-input-the-higher-the-yield-the-better-it-is” initiatives. And, both executed by classic agronomists and not by development workers/organisations. Of course, the ‘conclusion’–if it is correct to grace the outcome in this way–by Mr Bolliger would seem valid for your argumentation and for his own research, but should never have been used in the context of this paper.

“The response of many CA proponents to such questions is simply to raise their hands and say ‘‘but what are the alternatives to CA?’’” (lines 849-851).

Please let me know if you know of any better. As a development worker, I need tools that work in practice and if you have found something(s) that work(s) better than CA, please, I need them!!!

Final remarks
One general questions we need to consider is how did smallholders in SAA get into the dismal situation that they live in? Certainly, this is partially a historical and social question (e.g. overpopulation) and we cannot answer it only by looking to agriculture for an answer. However, many smallholder fields in SSA are highly eroded, have poor soil fertility and indeed are not suited to crop production. These circumstances partially result from wrong cropping practices using the plough and overstocking as in the case of the Eastern Cape Province, South Africa. Using the Einstein dictum, that problems cannot be solved within the mind-set that created them, we might need to first analyse if other cropping practised (other than CA) hold an answer, but should not refer back to the “problem creating mind-set” of the plough as you did in line 853 by stating “Perhaps one possibility is the plough… .” Please see my comments at the end of the second paragraph of the football example.

Here I can also see a problem of research. Already during the 70s and 80s, it became clear that conventional agricultural research was largely irrelevant to the circumstances of smallholder famers. As indirect proof of this, we can review the dates when development literature started question the existing paradigms (among expert research workers) and started calling for a shift towards farm system research (FSR), participatory research, etc.

Anybody that has been on smallholdings will know that many external factors influence the activities and decisions of farmers. As one friend from Uganda once said to me, a smallholder’s farming systems reaches from a framer’s (his/her) own bed to the farthest living relative they have (e.g. in the UK). We can also understand with this example that each farming system is different (each bed is different and relatives might be living on the same farm, in the capital or a foreign country). To apply now a simplistic, reductionist basic research system to complex systems misses the point entirely. CA is a production system or even “more correctly”, it is a different way of doing agricultural production.

In repeating myself, what we often see in the field and which is passed of as ‘research on CA’ is research already constrained and deformed by badly practiced CA principles; or research reduced to measuring just CA to one principle; or research that does not apply all three principles simultaneously and continuously. In short, the kind of non-systems ‘science’ that you plead for in your paper. Again, I refer to my “Football” and “Car Driving” examples.

Nonetheless, we can also not expect to rectify decades, perhaps centuries, of bad farm management practices within 1 or 2 years of adopting of CA. Most problems of smallholders have far deeper roots than could be changed by a change of agricultural production systems. A holistic and interdisciplinary approach to rural development should be applied in general, which many organisations, local, provincial and international, do not do.

Likewise, because CA is a system where the basic three principles must to be applied simultaneously and continuously, it takes at least 4 to 5, but rather 7, years before the real soil advantages of CA are manifested (see e.g. Riezebos & Loerts, 1998). Most development projects, which are the cutting edge of development (Gittinger, 1984), or development interventions, as they should be called, have a shorter timeframe, as I mentioned in a paragraph above. Therefore, can we expect to experience the CA advantages in such interventions? I refer here to my “Time” principle.

I think that your chapter 4.3 supports my argument very strongly. Personally, I think that this chapter is the best part of you paper.

Overall, I do not think that this paper presents either a fair or a logical assessment of the potential of CA to SSA farmers. You base your arguments on too many bad research examples, admittedly, because real good CA examples in SAA are scarce or are not documented in peer reviewed scientific papers. Furthermore, the comparison between South America and SAA is, all too often, a straw man comparison between ‘Apples and Oranges’. The experiences in South America for smallholder CA need to be used, but instead, the existing South American literature is almost entirely absent in your paper. That you did not even mention Herbert Bartz’s work, is tantamount to writing about Hamlet without mentioning the Prince.

To me, it seems that CA has finally arrived in the world of ‘development science’–a few decades after farmers in Brazil saw the light. We should not forget that development is seen by many as a ‘business’ in which development stands for a personal development, financially and expert-wise, and sustainability becomes a process to secure ones own job and future. The notion of helping the poor is too often forgotten or ignored. Consequently, the wrong approach for development interventions is too often used; because, widely, development work has become an end in itself.

In spite of all this, and the fact that your paper asks a good question badly and answers it even more poorly, I can find a silver lining in the revelation that CA needs competent inquiry and that it must not and cannot be seen as a silver bullet. In support of the latter, I use the example from Paraguay, where CA is seen as “base productiva” from which development can start to become sustainable, but nothing more. Other interventions and components of development work have to follow or be applied at the same time, e.g. agro-forestry, value adding, securing markets etc. However, if at the end of the day soils erode and their fertility declines–as happens with ploughing–no other agriculture/development intervention will be sustainable and succeed in the long-term.

I hope that you understand the points that I tried to make? To me, CA is a tool that works well to facilitate development, the best I have found to date. CA works everywhere where agriculture/crop production is compatible with the natural conditions, but there again, we face the problem that agriculture went into areas/regions, where perhaps it should never have gone. Most problems that you address or criticise or question are developmental or extension issues and not related to CA per se.

Badly practiced CA, unfairly written and illogical papers like yours make my work very difficult, because ill-informed opponents, or people who pursue their own agendas, e.g. in local research institutions who will always join the call for ‘more funds for better research’ or, perhaps, government officials divorced from practical realities, like to take papers like yours and use them against us who are concerned about financially-resource-poor farmers. I hope that you can reconsider your position and opinion and you could have a look at the other side of the coin. I understand that you need to produce papers for you work, but please be fair and logical in the future.

BOLLIGER, A. (2007). Is Zero-till an appropriate agricultural alternative for disadvantaged smallholders of South Africa? A study of surrogate systems and strategies, smallholder sensitivities and soil glycoproteins. PhD Thesis. University of Copenhagen, Copenhagen.

Thanks for your considered response to our article on CA. You make your points very clearly. It is a pity that the debate on CA is so polarized, it seems that only two positions are possible – either for or against CA. As you seem to appreciate, the aim of our article was to open the middle ground for debate. We do not say that CA does not work or that it cannot work, we simply ask the question if it always is the most appropriate technique for farmers in SSA. You clearly on basis of your experience have come to the conclusion that it is. Fine, but then please show it. You write that our paper is neither fair nor logical and is based on “bad research examples” because as you write “real good CA examples in SAA are scarce or are not documented in peer reviewed scientific papers”, which is exactly what we found when we went through the literature for our paper. If you think that our paper is biased we invite you to publish a response which in a non-biased way discusses the experiences of CA in SSA. In the mean time we can’t help wondering that if there are so many “real good CA examples in SSA” why they haven’t been reported.

Please do not exagerate the amount of people that are against CA. Probably you, the opponents, are a rather small group. And do not believe that only peer reviewed papers are of value in technology development, that is a very science oriented view. If only peer reviewed papers are of value than a farmers experience is probably worth nothing, because he does not write peer reviewed papers.

I agree entirely with you (and Dirk Lange) that the value in technology (or any other type of) development is not in whether or not it appears in peer reviewed papers – far from it. But normally experiences and developments that take place outside of the scientific community do find there way into the scientific literature. Given the amount of attention that CA has received at all levels I would however have expected that experiences, both positive and negative, will have been reported. The surprise that I expressed is that the studies that there are on CA in SSA are far from being unequivocally positive (see our review). I don’t think that this is due to a bias against SSA within (parts of) the scientific community as suggested by Dirk Lange, but due to a lack of evidence. Given that lack of evidence is it really justified – and fair to the farmers in SSA we are trying to help – to promote CA as stronlgy as is being done by its proponents?

just two things to clarify: (i) I did not suggest that there is a bias against SSA within (parts of) the scientific community. (ii) “studies … CA in SSA are far from being unequivocally positive”, here I questioned if the CA researched on was or is really CA.

What Ernst meant in his message is: The fact that studies on CA in SSA are not unequivocally positive (our review) is not due to a bias against CA in SSA within (parts of) the scientific community (as suggested by Dirk Lange).

Those colleagues that are as long as I am in this CA/No-till business will recall the early days of no-till in Brazil in the 1970’s when in general the scientific community was very skeptical towards no-till and many scientific papers kept pointing to the problems instead of offering solutions, the same as you do today. Does CA/No-till have problems? Yes there are. But you can have two attitudes towards a problem.

1. How can we solve the problem? Let’s get to work to resolve it.

2. Oh, there is a problem, you see it does not work!

Unfortunately scientists are not always good at developing agricultural production systems and solving problems of farmers. The no-tillage development in Brazil is a proof of this. If today there are 5.7 Million ha (80% of the cropping area) of no-till in the State of Paraná and 25 Million ha in Brazil, it is essentially because farmers made it work and promoted the technology. A significant part of the scientific community was very skeptical way into the 1980’s until the exponential growth of no-tillage in the 1990’s, that means the facts, persuaded most of the skeptics. The whole country is now > 70% no-till.

Brazil is not an exception, a similar situation occurred in many countries of the world. Australia is one example. Researchers demonstrated in the 1980’s that no-tillage does not work and would not be a choice for Western Australia. Until pioneer farmers made it work and promoted it through their Western Australian No-till Farmers Association (WANTFA) with the result that today 92% of Western Australia’s cropping area is under no-till.

These examples show that not only in SSA studies on CA/No-till have been always UNEQUIVOCALLY POSITIVE, but despite this fact the system has been successfully developed by farmers and those interested in sustainable agriculture.

Back to your question: “Given that lack of evidence is it really justified – and fair to the farmers in SSA we are trying to help – to promote CA as strongly as is being done by its proponents?”

My answer is yes. And probably you (Giller et al) will permanently owe us the answer to the question of which technology could be promoted instead if our goal is to achieve sustainable agriculture and this is a must in the 21st century.

Thanks for you reply.
Just to reiterate what we already have stated: We do not say that CA cannot work nor that it always is unsuitable in a SSA context. Discussions on that point divert from the main issue we try to make in our article: What is the socio-ecological niche for CA in SSA? (see the conclusion). Defining that would be of great help to know what technology (and CA is just one of many), or indeed what approach, might be most appropriate in a specific setting.

To answer your last question: The answer is not to try to find the technology that will prove to be the silver bullet, but lies in paying more attention to the socio-economic, cultural and ecological context in which farmers operate and that defines the limits for what types of development are possible in a given setting.

My first Zero Tillage in 1976, of maize into a Centrosema seed crop, was a total failure because I did not foresee a serious weed problem with the annual Digitaria insularis species and there were no selective herbicides. This cost me my job, because my groundbreaking tropical forage seed project, with 1000ha of ten tropical forage legumes, was closed by Shell in 1977 and I went to Goias to plant soybeans. After four years of fighting erosion with conventional tillage, I decided that Zero Tillage simply had to work, so I bought a ZT planter and made it work. As Rolf relates, the given opinion of researchers and extension and even practitioners from Rio Grande do Sul was that it would not work on Cerrado soils because of compaction and lack of winter rainfall. Now 90% of tropical soybeans are under Zero Tillage. Two or three researchers got on board after I demonstrated differenytsystems on-farm in 1988-92. It took the president of Embrapa, Alberto Duque Portugal, to stand up in the 5th National Brazilian Zero Tillage conference (Goiania, 1996) and exhort his researchers to catch up with the farmers, and there was still resistance even after that,

But, looked at in a positive light, problems are challenges, not blind alleys. They can be solved if they are correctly and impartially diagnosed and a large dose of persistence is applied to their solution. When farmers feel the benefits of zero Tillage in their boots, they get on with it and make it work, through successive attempts at a solution. And they are never satisfied, always trying to do more. What research has done in Brazil is to refine the solutions, define the parameters for success and produce high-yielding varieties which generate more profit. This is necessary to generate risk capital for the pioneer farmer to go on pushing out the limits of the technology – and unearthing problems for research to solve.. The story of Herbert Bartz is one of extreme persistence and application of logic to his observations; he was driven by the faith that he was on the right road and was in close contact with research.

Norman Borlaug once said to me “Researchers need to be close to the farmer, because that is where the truth lies”. (And please don’t quote me out of context as saying “…..the truth lies”!)

Thank you for your response from which I quote: “…the main issue we try to make in our article: What is the socio-ecological niche for CA in SSA?”

The discussion if CA/No-till would be suitable only for one or the other target group or socio-ecological environment was carried out here in South America already some 25 years ago. The experience in South America has shown that there is no specific socio-ecological niche for CA. What CA researchers, development workers and farmers need to do is to tailor the technology for the different socio-economic groups in the different agro-ecological regions of SSA. Agricultural production systems are always site specific but the principles apply everywhere. Of course attention has to be paid (as with any technology or innovation) to the socio-economic, cultural and ecological context in which farmers operate.

This was a message sent by Peter Aagaard. He has a PDF file that you can request by emailing him at paagaard@zamnet.zm

Re: Misconceptions about MT and CF – East & Central Africa

As there has been a lot of discussion about CF/CA recently I thought it would be useful to clarify what I consider to be a number of common miconceptions. Being a farmer myself and having worked with small-scale farmers since 1968, I thought it would be useful to challenge some of these ideas from a ‘farming’ rather than a research perspective.

We get a lot of visiting consultants through here who arrive with fixed ideas which need to be questioned! The document contains a lot of photographs as I think this is the best way to expain my points.

Together with some colleagues, I established the Conservation Farming Unit in 1996 to promote CF/CA among smallholders. We probably have the largest programme in Africa and tens of thousands of adopters will tell you they are more food secure, more productive and get better results in both normal and adverse seasons than they did before.

The following comment was made by Christian Roth in response to Peter Aagaard’s paper above. This is worth requesting at paagaard@zamnet.zm

Hi Peter,

Thanks, a very interesting read. The upshot – its horses for courses, and we need to accommodate the realities of low and erratic rainfall, labour availability and competition for residues in most of semi-arid Africa. All will take time and in my view cannot be achieved in a ‘step function’ transition from traditional farming systems to CA – there will have to be intermediary steps in many cases, and these may not resemble the CA principles in their full extent.

There is a lot of published data now available in journals that shows CA adoption does result in increases in SOM. Data varies with some reporting surface increases and others at greater depth. By reducing tillage, you reduce SOM oxidation and don’t disturb biological processes. By keeping a permanent soil cover, you promote biological activity while adding organic matter.

There is a lot of literature coming out these days that show if you reduce or even eliminate tillage and keep a permanent vegetative cover, that soil organic matter will increase. Maybe more in the upper layers of the soil first, but with time, lower in the profile. Just need to read some of the papers you can find on our web site at http://conservationagriculture.mannlib.cornell.edu/